Non-invasive measurement of physiological parameters or substance concentrations in human tissue

ABSTRACT

A device for optical detection of analytes in a sample includes at least two optoelectronic components. The optoelectronic components include at least one optical detector configured to receive a photon and at least one optical emitter configured to emit a photon. The at least one optical emitter includes at least three optical emitters disposed in a flat, non-linear arrangement, and the at least one optical detector includes at least three optical detectors disposed in a flat, non-linear arrangement. The at least three optical emitters and the at least three optical detectors include at least three different wavelength characteristics.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/396,556, filed Aug. 6, 2021, and titled “DEVICE AND METHOD FORDETERMINING A CONCENTRATION IN A SAMPLE,” which is a continuation ofU.S. patent application Ser. No. 16/570,615, filed Sep. 13, 2019, andtitled “DEVICE AND METHOD FOR DETERMINING A CONCENTRATION IN A SAMPLE”(now U.S. Pat. No. 11,085,876 issued Aug. 10, 2021), which is acontinuation of U.S. patent application Ser. No. 15/109,658, filed Jul.5, 2016, and titled “DEVICE AND METHOD FOR DETERMINING A CONCENTRATIONIN A SAMPLE” (now U.S. Pat. No. 10,416,079 issued Sep. 17, 2019), whichis a U.S. national stage application under 35 U.S.C. § 371 ofInternational Patent Application No. PCT/EP2014/078466, filed on Dec.18, 2014, and titled “DEVICE AND METHOD FOR DETERMINING A CONCENTRATIONIN A SAMPLE,” which claims priority to German Patent Application No. 102014 100 112.5, filed on Jan. 7, 2014, and German Patent Application No.10 2014 101 918.0, filed on Feb. 14, 2014. The International PatentApplication was published in German on Jul. 16, 2015, as PCT PublicationNo. WO 2015/104158. The entire contents of each of the above-identifiedapplications is expressly incorporated by reference herein in itsentirety for all purposes.

BACKGROUND

There are known arrangements and apparatuses for optical in vivomeasurement of analytes in samples, such as biological tissue. They arebased on spectroscopic procedures in which light is radiated into thesample, passes through it and emerges from the sample at a differentlocation. The attenuation of light resulting from absorption anddispersion is measured at the point of exit by a detector. Usingappropriate reference measurements, the concentration of analytes can bedetermined from this measurement.

Since the detected signal is dominated by the dispersion, particularlyin biological tissue, procedures are used to separate absorption anddispersion. They have spatially separated detectors to which each isassigned at least two emitters at different distances, which createsmultiple emitter-detector pairs which can be compared with each other inregard to their distances. If this takes place for one or multiplewavelengths, the concentration of the analytes can be determined with aspecial computation of the measurements. An example of such anarrangement is described in DE 4427101 (Hein).

Different optical path lengths are often measured. The properties in alocation in the sample to be examined can be concluded based on shorterand longer optical path lengths from the comparison of measurementresults.

This procedure is known and disclosed under the SRR Method.

The preliminary processing of measurements is a common practice, e.g.,with differential measurements between light and dark measurements withpulsed lighting or with the averaging of multiple measurements.

Procedures that weight the measured light intensities with 1/r²(r=distance between LED and optical receiver) or logarithmically weightthe light intensity are also common practices.

A comparison of different wavelengths by subtraction or formation ofquotients is also common.

The weighted summation of processed measurements obtained in this mannerin order to be able to deduce the concentrations of specific substancesin the sample to be examined is also common practice.

The determination of weighting factors of the evaluation algorithm inorder to adapt the output values of an evaluation algorithm withmeasured raw data to measured reference data is also common practice.

It is also common that such reference data can originate from testsubjects and from artificial phantoms.

The transfer of calibration data of a measuring system using skinphantoms to a second measuring system is also common practice.

The indicated procedures have not been suitable for far-reachingcommercial application, e.g., for measurement on human skin tissue. Thisis due to the fact that the quality of the measuring method isinadequate. Some approaches have already been proposed as a solution. Anattempt was made to eliminate the surface inhomogeneity of the tissuewith a specific computation, e.g., U.S. Pat. No. 7,139,076 (Marbach). Inthis approach, the assumption was that the irradiation of light on thetissue is rotationally symmetrical for all solid angles and can bereceived by the detector in the same manner.

With targeted irradiation of the light on the tissue with an angle ofincidence of 5° to 85° to the surface of the tissue, DE 10163972achieves better homogeneity conditions for the measurement and thus amore precise measurement result. Whereas WO 94/10901 (Simonson page 19)assumes that the detection angle for measurement has no significance, DE10163972 describes that the result improves when the detection alsotakes place at an appropriate exit angle from the tissue.

Particularly with respect to the repeat accuracy of successivemeasurements, the inhomogeneity of tissue and surface structure and theinhomogeneous distribution of analytes in the sample pose a problem thatcannot be solved with the known procedures and apparatuses. Withrepeated application of the device on the region of the tissue to bemeasured, a variation of the measuring location takes placeautomatically, which results in measurement deviations. Elaboratemeasurement location determination and relocation techniques that enablepositioning of the device on an early measuring position are technicallycomplicated and expensive. Therefore, the use of such techniques is onlybeneficial and possible in laboratory conditions. They are not an optionfor real-life use. Tissue areas with a different concentration of theanalyte and changed dispersion centres are also analysed in real-lifeuse with repeated measurement. This variation also unavoidably leads toa changed measurement result even with exact determination of theconcentration. A measurement result owing to the inhomogeneity of thedistribution of analyte cannot be compared with earlier measurementresults. Therefore, there is no clear answer to the question of whetherthe concentration of analyte has increased, decreased or remainedconstant. Consequently, no diagnosis can be derived from the result ofsuch series of measurements for medical applications. As a result,monitoring of concentration values is not beneficial with such a device.

There are additional problems with the anisotropy of the examinedsample. The surface structure, cell structure and, for instance, bloodvessels, are causes for the anisotropy of the sample. The majority ofthe known devices provide measurement values that depend on the angle ofapplication of the device on the sample. This also leads to measurementdeviations under real-life conditions.

There are additional problems with the detection of a specificsubstance, for instance, human tissue, in which a considerable number ofsubstances that also have an effect on the optical signals used for thedetection must also be taken into consideration. These substances alsocontribute to falsification of the measurement result. The quantity ofthese substances in the sample can vary greatly and also very rapidly.For instance, with heavy or light application pressure of the sample onthe device, there is more or less blood in the tissue, which clearlymakes the measurement pressure-dependent with known analyticalprocesses.

Therefore, a device and method that determine a correct and stablemeasurement result for the concentration of the relevant analyte oranalytes are needed. In the process, boundary conditions such as theinhomogeneity of the sample, the anisotropy of the sample, the presenceof a multitude of substances in the sample and varying conditions in themeasurement environment must be tolerated. The differences betweenrepeated measurements must be so slight that they do not significantlyaffect the measurement result.

SUMMARY

An aspect of the present invention is to determine the concentration ofan analyte in conditions that can be obtained in real life which do notlose their representative nature for the sample even with repeatedapplication of the device on the sample and with which the concentrationcan be determined with good reproducibility using the inventive methodand device. The system should also be technically unelaborate, portableand affordable to produce.

In an embodiment of the present invention, a device for opticaldetection of analytes in a sample includes at least two optoelectroniccomponents. The optoelectronic components include at least one opticaldetector configured to receive a photon and at least one optical emitterconfigured to emit a photon. The at least one optical emitter includesat least three optical emitters disposed in a flat, non-lineararrangement, and the at least one optical detector includes at leastthree optical detectors disposed in a flat, non-linear arrangement. Theat least three optical emitters and the at least three optical detectorsinclude at least three different wavelength characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basisof embodiments and of the drawings in which:

FIG. 1 shows a simple emitter-detector arrangement;

FIG. 2 shows an emitter-detector arrangement in the form of a matrix;

FIG. 3 shows an emitter-detector arrangement in the form of amatrix-representation of 24 short optical paths;

FIG. 4 shows an emitter-detector arrangement in the form of amatrix-representation of 16 short to medium-length optical paths;

FIG. 5 shows an emitter-detector arrangement in the form of amatrix-representation of 32 different medium-length optical paths;

FIG. 6 shows an emitter-detector arrangement in the form of amatrix-representation of 12 long optical paths;

FIG. 7 shows an example cross-section of a device housing;

FIG. 8 shows a housing with positioning aids for measurement on the ballof the thumb of the hand;

FIG. 9 shows a housing with positioning aids for targeted movement ofthe device on the surface of the measurement object;

FIG. 10 shows an example configuration of the device;

FIG. 10 a shows an example arrangement of emitters and detectors;

FIG. 10 b shows an example of equal emitter-detector pairs;

FIG. 10 c shows an example of equal emitter-detector pairs;

FIG. 10 d shows an example of equal emitter-detector pairs;

FIG. 10 e shows an example of equal emitter-detector pairs;

FIG. 10 f shows an example of equal emitter-detector pairs;

FIG. 11 shows a description of electronic components—optical emitters;

FIG. 12 shows a description of electronic components—optical detectorevaluation circuit;

FIG. 13 shows a description of a device 1;

FIG. 14 shows a description of a device 2;

FIG. 15 shows a description of a device 3;

FIG. 16 shows a device with multiple arrays;

FIG. 17 shows a variant of a measuring circuit;

FIG. 17 a shows a measurement of one optical path;

FIG. 18 shows an arrangement with a rectangular arrangement of the lightbarrier;

FIG. 18 a shows a directional characteristic implemented by using arectangular shape;

FIG. 18 b shows a directional characteristic implemented by using arectangular shape;

FIG. 18 c shows a directional characteristic implemented by using arectangular shape;

FIG. 18 d shows a directional characteristic implemented by using arectangular shape;

FIG. 18 e shows a directional characteristic implemented by using arectangular shape;

FIG. 19 a shows an increase of spectral resolution by using combinationsof different optical emitters with different optical detectors;

FIG. 19 b shows an increase of spectral resolution by using combinationsof different optical emitters with different optical detectors;

FIG. 19 c shows an increase of spectral resolution by using combinationsof different optical emitters with different optical detectors; and

FIG. 19 d shows an increase of spectral resolution by using combinationsof different optical emitters with different optical detectors.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

If the inhomogeneity of a sample is a problem, the person skilled in theart often solves this by conducting multiple measurements at differentlocations on the samples. This can take place with successivemeasurements, which often makes the measurement time-intensive, makingit unbearable for economic or comfort reasons. One approach is tointegrate several emitters and detectors that are arranged side by sidein one measuring device. Corresponding publications can also be foundfor the indicated application case.

For consideration of the inhomogeneity in the depth of the sample, thereare approaches that work with different distances between light emittersand light detectors, but must be greatly improved in order to be useful.

For the approach to the problem of anisotropy, several measurements atdifferent angles would be a possible solution.

For detection of interfering substances, lighting with a larger numberof monochromatic light wavelengths is known. A spectroscopic examinationof the light exiting the sample is also a known solution for determiningthe influence of interfering substances.

However, it is not possible to combine these techniques, because amultitude of measuring lengths would be required. Since the device foranalysis of the sample cannot be larger than the sample itself, andbecause detectors and emitters must have certain areas in order tofunction, there is, despite advancements in miniaturisation ofmicroelectronics, no known solution for integrating a sufficient numberof measuring path lengths, light emitters having different wavelengthsand different orientations of measuring paths in the device required forthe measurement.

The invention explained here describes how the problem can be solved andwhich method can be used for operation of the device.

The inventive approach for optical detection of analytes in a sample ischaracterised in that the device has three emitters for emission ofphotons in a planar arrangement, not in a line, and at least threedetectors for receiving photons in a planar arrangement, not in a line,and that the emitters and/or detectors have at least three differentwavelength characteristics.

The terms ‘photons’ and ‘light’ are used synonymously in the scope ofthis document.

With a suitable planar arrangement of light emitters and detectors,multiple use of components is made possible. This multiple use makes itpossible to succeed with a lower total number of emitters and detectors.

According to the invention, with the arrangement of components on theplane, a large number of different distances between emitters anddetectors can be achieved with a relatively low number of components.The optical properties at multiple, significantly different points canbe determined as a result. Measurements with different orientations canalso be carried out as a result. In addition, a high spectral resolutioncan be achieved with a reduced number of components.

With use of a measuring circuit according to the invention, anadditional increase in the amount of information is achieved without theneed to increase the number of optical components. The circuit has avery high dynamic range that permits use of longer and shorter opticalpath lengths than is possible with circuits having comparable technicaldifficulty, causing the number of usable light emitters and lightdetector pairs to increase while the number of light emitters and lightremains the same.

With beneficial optical geometry, the amount of information is furtherincreased and the measurement result becomes more precise. With adirection-dependent variable emission characteristic, a determination ofthe analyte can also take place with a concentration that varies in thedepth of the sample. As a result, the measurement result can be furtherimproved.

With a method for combining emitters having different wavelengthcharacteristics with detectors having different wavelengthcharacteristics, a high spectral resolution of the measurement isachieved with a low number of components. Therefore, it is possible toreduce the influence of substances in the sample that manipulate themeasurement value.

Furthermore, a method is explained with which the evaluation of theindicated multitude of information is implemented in an advantageousmanner.

With a combination of the evaluation process with the inventivearrangement of the measuring device, a usable measuring system can alsobe practically implemented in real-life environments. With a combinationof the indicated method, it is surprisingly possible to incorporate allcomponents required for a repeatable precision of the measurement on theavailable surface limited by the sample. The inventive measuring systemis even small and compact enough that it can be integrated in real-lifeobjects or also be used as a portable pocket-sized device.

In an advantageous version, the system can be arranged as an electronicprinted circuit board and does not require any optical fibres.Therefore, it can be realised affordably in a small format.

It is surprising for the person skilled in the art that a symbiosisbetween the two approaches is created, which still does not have asignificant influence on the overall system with a slight increase inthe number of components. However, if a system is designed according tothe rules below, the symbiosis for larger numbers of componentsincreases disproportionately and the demands explained at the outset canthus be resolved on the surface available for the optoelectronics.

The intended generation of this symbiosis and the resulting possibilityof generating a basis of information increasing disproportionately inquantity and quality in relation to the number of emitters and detectorsthat are used together with the method of this basis of information tobe evaluated are the most important basic ideas of the presentinvention. In order to achieve the desired symbiosis, it is advantageousto exceed a number of components specified further below in the text andto follow the specified geometric arrangement rules.

The solutions addressed in the preceding text are explained in detailbelow.

According to the invention, the device consists of at least threeemitters in a planar arrangement that are not in a line and at leastthree detectors in a planar arrangement that are not in a line and theemitters and/or the detectors have at least three different wavelengthcharacteristics.

In a preferred variant, there are at least six emitters in a planararrangement that are not in a line and, additionally preferred, at leastsix detectors in a planar arrangement that are not in a line and theemitters and/or the detectors preferably have at least three differentwavelength characteristics.

In an alternative variant, there are at least 50 or 100 emitters in aplanar arrangement that are not in a line and preferably at least fouror eight detectors in a planar arrangement that are not in a line andthe emitters and/or the detectors preferably have at least three or fivedifferent wavelength characteristics.

The device preferably comprises at least two or three detectors havingdifferent wavelength characteristics and at least two or three emittershaving different wavelength characteristics. The wavelengthcharacteristics are preferably wide band, such that more differentwavelength characteristics can be created by combining differentemitters with different detectors than the larger number of detectors oremitters of different wavelength characteristics.

The device preferably consists of pairs that each have an emitter and adetector that have an approximately equal distance between emitter anddetector and approximately equal wavelength characteristic. In the scopeof this document, the term ‘equal emitter detector pair’ or ‘equal pair’or ‘group of equal pairs’ preferably refers to multiple emitter-detectorpairs that each have exactly one emitter and exactly one detector andhaving an emitter-detector distance that is approximately the same andthat have approximately the same wavelength characteristic.

The terms ‘equal pairs’ and ‘comparable pairs’ are used synonymously inthe scope of this document.

It is preferred that the emitters and/or detectors are members in atleast two, preferably at least six such pairs.

At least one emitter and/or detector or multiple emitters and/ordetectors or all emitters and/or detectors are members in at least twoor at least six different groups of equal pairs.

The device preferably comprises equal emitter-detector pairs havingconnecting lines that do not exclusively run in parallel.

The device preferably comprises equal emitter-detector pairs—preferablyalso at least equal emitter-detector pairs—in which the orientation ofconnecting lines with a virtual intersection on a two-dimensional planeresults in an acute angle of 30° to 45° or preferably an angle of >45°and especially preferably an angle of 90°.

The emitters and detectors are preferably arranged such that sufficientcoverage of all necessary orientations of the connecting line betweenemitter and detector and/or between detector and emitter is provided forthe relevant values of distance and wavelength characteristic. It isespecially preferred if the orientations do not differ for any angle bymore than 180 degrees, preferably 120 degrees and ideally 70 degrees. Itis especially preferred if between 3 and 5 orientations are created,preferably between 4 and 8 orientations, that are distributedapproximately equally on the angle scale. Since this cannot always beachieved due to additional boundary conditions according to theinvention, in a preferred arrangement, at least one arrangement isselected for at least one part of the groups of comparable optical pathsin which there is at least one connecting line within each angle rangeof a defined angle sector width, wherein the orientation of saidconnecting line falls within the angle range. The width of such an anglesector is no higher than 180 degrees, preferably 120, 70, 50, 20 or even10 degrees.

The device preferably consists of emitter-detector pairs—preferably alsoequal emitter-detector pairs—that satisfy a surface-based distancecriterion and/or a volume-based distance criterion and/or anorientation-based distance criterion. Preferably, multiple or all equalemitter-detector pairs satisfy one or multiple of these distancecriteria.

The device preferably comprises a device for influencing the emissiondirection of the photons emitted by the emitters.

The device preferably comprises a device with which the influence ofreception directional characteristics of the detectors takes place.

The device preferably comprises means that produce the effect that thephotons emitted by the emitters and/or the photons detected by thedetectors are not emitted and/or detected rotationally symmetrically.

The device is preferably configured such that the photons emitted by theemitters are essentially emitted at an angle between 5° and 90° to theplane on which the emitters and detectors are located and areessentially received at an angle between 5° and 90° to theaforementioned plane of the detectors.

The device preferably comprises emission and detection angles that areproduced by a rectangular geometry of emitters, detectors and/or photonguide elements.

The device is preferably configured such that different directionalcharacteristics in the sense of a far field radiation/receiving patternare achieved through different orientations of the components and/orchips of the emitters and/or detectors to the plane spanned by theemitters and detectors.

The device is preferably configured such that different directionalcharacteristics are achieved by refracting and/or diffracting and/orreflecting and/or shadowing the emitted and/or detected photons.

The device is preferably configured such that, for at least onewavelength the distances between the detectors and emitters provided forsaid wavelength in the range of distances between detectors and emittersthat are short enough for use are arranged in a finer gradation than fora different wavelength, wherein the distances are shorter than the otherwavelength by a factor of 0.9 or 0.8 or 0.6 or 0.3.

The device preferably comprises optoelectronic components arranged in amanner such that length differences for a wavelength arise which aresmaller than the detector size, the emitter size or the distance fromdetector to emitter, and particularly such that the optical path lengthdifferences are only 50% or 20% or 10% or even 5% of these sizes.

The device preferably comprises optoelectronic components that arearranged such that distances between detectors and emitters arise, saiddistances having length differences that are less than twice thedetector distance, less than the single detector distance or less than55% of the detector distance.

The device preferably comprises optoelectronic components that arearranged such that the number of significantly different distancesbetween detectors and emitters is greater than the number of detectorsor the number of emitters or the sum of both. ‘Significantly different’means that the optical paths differ by at least an amount that isgreater than the closest distance between two detectors or the closestdistance between emitters or the larger of these two values or the sumof these two distances. In an advantageous variant, said distancebetween components is defined by the distance between the areasassociated with these components where the light enters or exits thesample. In an advantageous variant there is opaque material in theregion of this distance.

The device is preferably configured such that the surface of thearrangement is not planar or is comprised of multiple detector elementshaving different orientations.

The device preferably comprises some optical components that arearranged such that they can be moved with respect to other opticalcomponents.

The device is preferably configured such that the device has a contactsurface that can be brought into direct contact with the sample to bemeasured.

The device is preferably configured such that it is suitable for cominginto contact with biological material, particularly human or animaltissue. In an advantageous variant it consists of material that is easyto clean. In an advantageous variant it consists of material that ishighly resistant to chemicals.

The device is preferably configured such that the control electronics ofat least a part of the emitters has a matrix structure.

The device is preferably configured such that the control electronics ofat least a part of the detectors has a matrix structure.

The device is preferably configured such that the detectors have adynamic range of at least 1:100, a particularly preferable range of atleast 1:50,000, additionally preferable range of at least 1:1,000,000and further preferable range of at least 1:10,000,000.

The device preferably comprises evaluation electronics that enable theaforementioned dynamics.

The device is preferably configured such that the emitters and/ordetectors comprise semiconductor elements.

The device is preferably configured such that the semiconductor elementsare positioned no further than 50 mm, preferably no further than 6 mmand particularly preferably positioned at a distance of less than 1.5 mmfrom the sample when the device is in its measuring position.

The device preferably comprises sensors and/or data interfaces foradditional environmental conditions and/or physical or chemicalparameters and/or living circumstances of the sample belonging to theorganism.

The device preferably comprises means for influencing the measurementand/or environmental conditions, particularly heating, drying and/orcontact pressure application devices.

The device is preferably configured such that it can be integrated intodevices that have different functionalities and belong to the followinggroup of devices: smart phone, household appliance, personal scale,vehicle steering wheel, article of clothing, jewelry, tool, handle,furniture, toilet seat, input device.

In a preferred variant, the device is integrated in an object with whichthe user regularly comes into contact.

The device preferably comprises means for positioning relative to asample.

The device is preferably configured such that it enables the detectionof carotenoids and/or antioxidants and/or blood constituents and/orsubstances appearing in human or animal tissue and/or physiologicalrelationships and/or liquid and/or solid and/or gaseous substances.

With the inventive method for optical detection of analytes in a sample,particularly consisting of animal or human tissue, photons are radiatedinto the sample by at least three emitters arranged on a plane and notin a line. A portion of these photons exiting the sample is detected byat least three detectors arranged on a plane and not in a line, whereinthe pairs of emitters and detectors that are used have at least threedifferent wavelength characteristics and the concentration of analyte isdetermined from the analysis of measurement values of the detectorsusing mathematical methods.

With the method for optical detection of analytes in a sample,preferably at least three emitters preferably arranged on a planeradiate into the sample. The emitters preferably have differentwavelength characteristics and are preferably not arranged in a line.The photons exiting the sample are preferably detected by at least threedetectors which preferably have different wavelength characteristics.The concentration of analyte is preferably determined from the analysisof the photons exiting the sample using mathematical methods.

It is additionally preferred that a method in which the photons that areemitted by an emitter—preferably exactly one emitter—are detected by atleast two detectors having different wavelength characteristics and/orthe photons emitted by at least two emitters having different wavelengthcharacteristics are received by exactly one same detector.

Preference is furthermore given to a method that uses a mathematicalresult calculated from the detected photons of various emitter-detectorpairs that have an approximately equal distance and approximately equalwavelength characteristics to determine the concentration of analyte.

Preference is furthermore given to a method that uses a mathematicalresult calculated from the detected photons of various emitter-detectorpairs that have an approximately equal distance and approximately equalwavelength characteristics and radiation/receiving patterns withcomparable effect to determine the concentration of analyte.

Preference is furthermore given to a method with which representativevalues are determined for emitter-detector pairs having approximatelyequal distances and equal wavelength characteristics and, in anadvantageous variant, additionally with directional characteristicshaving a comparable effect—preferably for at least almost allemitter-detector pairs having approximately equal distances andapproximately equal wavelength characteristics and/or comparabledirectional characteristics—and the concentration of an analyte in thesample is determined and from these values.

Preference is furthermore given to a method that determines theconcentration of the analyte in the sample at different points using theamount of received photons at different wavelength characteristicsand/or various optical path lengths detected by the detectors. The totalconcentration of the analyte is then determined in consideration of themeasurement values for the various locations.

Preference is furthermore given to a method with which the photonsemitted by at least two emitters having different wavelengthcharacteristics are detected by at least two detectors having differentwavelength characteristics, so that measurement values are producedwhich have a number of wavelength characteristics that is greater thanthe larger number or the sum of the different wavelength characteristicsof the emitters and the detectors.

Preference is furthermore given to a method with which emitter-detectorpairs having approximately equal distances and approximately equalwavelength characteristics are averaged or mathematically combined witheach other in other ways, wherein said pairs satisfy a planar and/orspatial and/or orientation-based criterion.

Preference is furthermore given to a method with which values arerecorded multiple times in succession in order to detect and/oreliminate changes and/or fluctuations in the sample.

Preference is furthermore given to a method with which optical pathshaving different lengths between the emitters and detectors and/ordifferent locations and/or different emission characteristics are usedand for which the respective optical path measurement values arerecorded. It is preferable that the properties of the sample can beconcluded depending on the depth below a point on the surface by usingmathematical operations on the measurement values of these opticalpaths.

Preference is furthermore given to a method that compares the individualmeasurement values of a group of equal pairs or combines them with eachother with mathematical operations and determines a value characterizingthe fluctuation range of said pairs.

Preference is furthermore given to a method with which at least some ofthe emitters and/or detectors are used to determine measurement valuesat more than one measurement location.

Preference is furthermore given to a method with which the groups ofpairs having approximately equal distances and approximately equalwavelength characteristics are formed in which the emission anddetection angle of the emitter-detector pairs also have equalcharacteristics.

Preference is furthermore given to a method with which the exposure timeof the detectors corresponds to a multiple of the half periods of themains frequency.

Preference is furthermore given to a method with which the quantity ofphotons detected by a detector is measured, wherein the current throughthe optical detector is measured by discharging a capacitor andmeasuring the degree of discharge and/or the number of dischargingcycles within a short time and/or combining this with the measuring thecurrent directly.

Preference is furthermore given to a method with which at least two ofthe aforementioned methods for measurement of current are used.

Preference is furthermore given to a method with which the selection ofthe measuring methods which is used to measure the current through thedetector takes place automatically during the measurement. The selectionof measuring methods preferably takes place without the amount of themeasurement value to be expected being known before the beginning of themeasurement.

Preference is furthermore given to a method with which the measurementin each measuring mode takes place over a predefined time periodindependently of the measurement value.

Preference is furthermore given to a method with which the fluctuationrange of measurement values is determined by a sequence of measurementsin order to determine the minimum number of measurements necessary forthe respective sample, which minimises the deviations of measurementresults with successively conducted measuring cycles.

Preference is furthermore given to a method with which additionalinformation, such as temperature and air humidity of the environment,temperature of the sensor and/or the sample, is factored into theevaluation.

Preference is furthermore given to a method with which informationpertaining to the sample and the organism belonging to the sample isalso processed with the further processing of values obtained in themeasurement process. In particular, history of feed and/or nutritioncompositions, the quantity and history of stress situations, illnessesor environmental conditions are taken into consideration.

Preference is furthermore given to a method with which the individualbelonging to a sample can be differentiated with a certain probably fromanother individual by comparing the measurement results obtained fromthe sample of another individual.

Preference is furthermore given to a method with which the measurementresults are determined with an algorithm and algorithmic elements and/orconstants of the algorithm are determined with iterative calculations,preferably using a data processing system.

The arrangement can have various light emitters in an advantageousmanner, e.g., with various spectral characteristics.

The arrangement can have various detectors in an advantageous manner,e.g., with various spectral characteristics.

Preference is given to a rule for selection of positions of emitters anddetectors specified below, according to which it can be determined howclosely the illuminated regions of different pairs of emitters anddetectors may be arranged in order to maintain a high increase ofobtained information with an increase of the number of such pairs. Thepurpose of the rule is, among other things, to spare the pairings thatare not necessary according to the rule in order to utilise installationspace for, e.g., an improved spectral resolution. The methods explainedhere have a very close mutual interaction and cannot always be appliedindividually, as they need to be applied to the same geometricarrangement. However, in order to make the description clearer, theaspects must first be explained individually.

In an advantageous approach to the representative detection of theinhomogeneity of a sample, the arrangement and distribution ofemitter-detector pairs on a two-dimensional surface is configured suchthat there are emitter-detector pairs in which the path corresponding toa directly connecting line between emitter and detector are alsoapproximately equal. As already mentioned, such emitter-detector pairsare preferably identified as equal emitter-detector pairs. Anapproximately equal wavelength characteristic, for instance, is providedwhen the differences between two emitters are no greater than theproduction-related variation for each emitter. In the scope of thisdocument the distances of two pairs is called an approximately equaldistance between emitter and receiver, when the difference from theaverage path length of the two distances is a maximum of 30%, preferablya maximum of 20%, more preferably a maximum of 10% and ideally 5% orless. A group of pairs of approximately equal wavelength characteristicsand approximately equal distance consists of two or moreemitter-detector pairs. The more groups there are and the moreemitter-detector pairs that belong to a group, the better theinhomogeneity of the sample can be detected.

Preference is given to a variant in which the definition of whichemitter-detector pairs are to be considered as sufficiently equal formembership in a group of equal pairs is expanded with aspects oforientation of the emitter/detector connection line and/or thepreferable orientation of the paths of movement of photons and/oraspects of the directional characteristics of emitters and detectors.For the sake of linguistic simplicity, the explanation below usuallyonly addresses an approximately equal distance and wavelengthcharacteristic, because it is clear to a person skilled in the art aftermentioning the other criteria indicated above how to apply themanalogously.

Photons that wander from the emitter towards the detector pass through athree-dimensional space in the sample. The probability of presence in alocation in this space is related to the distance of this location fromthe direct connecting line between the two. At a large distance fromthis line, there are fewer photons than at a small distance.

With the examinations for representative consideration of theinhomogeneity of a sample, it could be determined in a surprising waythat with the distribution of emitters and detectors havingapproximately equal emitted wavelength characteristics on atwo-dimensional surface, the space through which photons wander can betaken into consideration in addition to the distance of emitters anddetectors in order to optimise the measurement result.

Preference is given to an approach with which the spaces through whichphotons wander at least 5%, preferably at least 20%, more preferably atleast 50% and even more preferably at least 80% and ideally at least 95%should not overlap.

Preference is given to a configuration of the invention in which theinstallation spaces that arise with the use of the distance criterionfor components are used in order to position components having differentwavelength characteristics.

The degree of overlapping of the spaces can be determined as follows:

Initially, the probability of the presence of a proton for each opticalpath to be considered between emitter and detector is determined foreach spatial element of the sample. In an advantageous variant, thisvalue is then based on a reference variable. This can, for instance, bethe average probability of residence of an equal-size volume element ofthe overall sample belonging to the same optical path, or also themaximum probability of residence of a photon on a volume element of thecentral plane between emitter and detector or also a constant. Acharacteristic is determined from the characteristics obtained for eachvolume element from the probability of residence, on the basis of whichit is determined whether the volume element belongs to the optical pathor not. This decision can be binary, but also analogue. With volumeintegration over the sample volume, the volume of the optical path canbe calculated. For a comparison of two emitter-detector pairs, thevolume of the optical path is calculated separately for each pair. Thenthe volume of the overlapping region is determined. This can, forinstance, take place with product formation of the membershipcharacteristics of the volume elements for the individual pairs.Alternatively, a table that defines the membership to the overlappingregion depending on the two membership characteristics with respect tothe two emitter-detector pairs in consideration. Volume integrationyields the size of the overlapping region between two pairs.

If the volume of the overlapping region is compared in relation to thevolume of the optical path of one of the two pairs, the overlap isrepresented as a percentage. The overlapping limit values specifiedabove can be applied for this.

It is still important that the specified overlapping limit values cannotonly be applied for each individual optical path pair but can instead beapplied in an averaged consideration of all optical paths of acomparable group.

The overlap of a volume element can be defined in an advantageousvariant for the pairings of each pair with every other pair and then beused to calculate an overlapping overall characteristic of the volumeelement. This can, for instance, take place with formation of themaximum value or summation of the analyses in pairs. With volumeintegration of the overall characteristic, the size of the overalloverlapping region can be determined. With volume integration of thevolumes belonging to an optical path, an overall characteristic isobtained for the volume of the optical paths. These can be compared inrelation to each other in order to obtain an overlapping limit value towhich the criterion mentioned above can be applied.

In an advantageous variant the criterion for selected groups withcomparable emitter-detector pairs is carried out individually.

In an alternative advantageous variant, the criterion for selectedgroups with comparable emitter-detector pairs is carried out for groups.

The method described above for determining the overlappingcharacteristic is identified as a volume-oriented distance criterion.

In an advantageous variant, the movement directions of photons are alsotaken into consideration. If they are significantly different, a reducedoverlapping characteristic is calculated despite a high probability ofresidence of photons. As a result, better consideration of theanisotropy of the sample is achieved, as explained in another part ofthis document. This method is identified as an orientation-baseddistance criterion.

In a simplified process for determining and checking the overlap, thethree-dimensional space through which the photons wander from thelocation of radiation to the location of their detection, projected onthe plane on which the emitters and detectors are located. A surface onthis plane is determined for each emitter-detector pair on which allpoints of the surface have a distance of at least 0.2 mm, preferably 1mm, more preferably 2 mm, even more preferably 3 mm and ideally 5 mm toeach point on the direct connecting line. Two consecutive pairs arecompared with each other with respect to the overlap. The limit valuesmentioned above are applied to the overlapping surfaces.

In an alternative variant the spaces through which passage occurs in thesurface of the emitters and detectors are represented by suitableellipses.

The overlapping characteristic can also be applied in pairs for each twooptical paths in this surface-based distance criterion. However, it ismore advantageous to consider an average value for the entire group ofequal pairs.

In an additional examination, it was determined in a surprising waythat, with the distribution and assignment of emitters and detectors ona two-dimensional surface, the orientation of the direct connecting linebetween emitter and detector is important for detection of theinhomogeneity of a sample.

In an advantageous version, the distribution of emitters and detectorstakes place on this surface in a manner such that emitter-detector pairsarise in which the wavelength characteristics are approximately thesame, there is an approximately equal distance, the overlap of theirspaces through which photons wander takes place in an inventive way andwith which the orientation of their direct connecting line isapproximately equal. An equal geometric orientation of emitter-detectorpairs is provided when the paths of the direct connecting lines arevirtually brought to an intersection while maintaining their orientationon a two-dimensional surface and the resulting acute angle is no widerthan 30°. Special preference is given to a solution in which this angleis no wider than 10°.

In an additionally advantageous version, emitter-detector pairs havingequal orientation are mathematically combined with emitter-detectorpairs having a different orientation. The group of the other orientationincludes emitter-detectors pairs that do not differ from the pairshaving the same orientation with respect to their distance and emittedwavelength characteristics, but in that the virtual intersection of theconnecting lines results in acute angles between 30° and 45°, orpreferably over 45° and running ideally nearly perpendicular to eachother. The comparison provides a representative mapping of theanisotropy of the sample. As the studies demonstrated in a surprisingway, the comparison achieved a high repeat accuracy of the measurementswithout the necessity of positioning the device in the same location ofthe measuring area for the repeated measurement. This circumstance isthe result of the following relationship: When the measuring devicehaving the inventive distribution and orientation of emitters anddetectors is applied, the light propagates along optical paths that runin different preferred directions corresponding to the emitter-detectororientation through the inhomogeneities (in the sense of inhomogeneousvolume) of the sample. As a result of these orientations in biologicaltissue, the light passes blood vessels and skin grooves with differentangles. Consequently, the orientation in which the light passes throughthe tissue does not change significantly even with repeated applicationof the device with a possible different angle. Therefore, with asuitable evaluation, a comparable measurement result is produced evenwith repeated measurement.

With the number of emitters and detectors, their packing density on atwo-dimensional plane, their orientation and the radiation and detectioncharacteristics of emitters and detectors, both the measurementprecision and the repeat accuracy in determining the concentrationincrease according to the present invention.

In an advantageous version of the invention, the measurement with thedescribed arrangement is repeated at least once, but preferably multipletimes. Preference is given to a variant in which this takes placeimmediately after the first measurement without removing the sample. Ina different preferred variant, the sample is removed and re-applied, oran additional sample is applied. A third advantageous variant is acombination of both methods.

With comparison or by mathematically combining the multiple conductedmeasurements, changing components can be recognised and purposefullyevaluated. The suppression of changing signal components is alsopossible by averaging or mathematical operations. With this process, forinstance, the recognition of the pulse frequency in a living sample ispossible, as well as the suppression of the measuring error caused bythe pulse. With re-application of the sample, operating errors orlocation dependencies can be recognised and compensated for. Withmeasurement of different samples, sample errors can be recognised andcompensated for.

The term wavelength characteristic in connection with this document isto be understood such that an optical transmitter or detector or asubstance through which light passes will influence or process lighthaving different wavelengths differently. The wavelength characteristicpreferably describes which wavelength is influenced in which way,especially how strongly.

Based on the example of an LED, the wavelength characteristicspreferably describe the intensity of the produced light depending on thewavelength. An LED with a specified emission wavelength of 700 nmtypically also emits light at 705 nm or 710 nm; however, this typicallyoccurs at a lower intensity. LEDs can, in particular, have the samespecified emission wavelength but, for instance, differ in theirwavelength characteristics such that they have narrower or widerwavelength characteristics. An example of this is a 700 nm LED thatstill has 50% of the maximum emission at 750 nm in comparison with anLED that only has 5% of the maximum emission at 750 nm. Examples forwavelength characteristics are illustrated and explained in FIG. 19 .The same applies for detectors.

In this document, the wavelength characteristic of a component does notonly refer to the characteristics of the actual chip. Filters, dyes,cast materials, assembly and installation situation, conditions of usesuch as temperature and age, as well as optically acting elements suchas thin layers or light-refracting elements that also have an influenceon the wavelength characteristics are also meant in this connection,insofar as it is logical.

The joint effect of the wave characteristics of the emitter and detectorare to be understood in connection with the wavelength characteristicsof an emitter-detector pair.

Some emitters can emit light varying in wavelength. For instance, LEDscontaining multiple chips for different wavelengths are known. Suchemitters are preferably treated as separate emitters in connection withthis document. Preference is given to a variant in which only oneemitter is activated in the process. In an alternative advantageousvariant, multiple emitters are activated simultaneously. This isadvantageous, for instance, when the simultaneous measurement ofmultiple emitter-detector pairs enables parallel and thus quickermeasurement due to slight or easily calculable overlapping of wavelengthregions.

Some emitters are capable of changing their wavelength characteristics.Examples of this are, for instance, LEDs that emit different wavelengthswith different operating currents. There are similar detectors that are,for instance, available with tunable filters. Preference is given to avariant in which tunable components in connection with the presentdescription are treated such that the wavelength characteristics of theemitter-detector pair is averaged or calculated during the time in whicha partial measurement takes place for a fixed wavelength characteristic.The duration of a partial measurement is thus defined in that a timesequence of measurement values is not obtained from the detector duringthis time.

A tunable emitter or detector can thus be virtually deconstructed andtraced back to the basic idea of this invention.

In connection with this document, the term directional characteristicshould be understood, in particular, as which quantity of light isemitted or received in which direction. The relationships basicallyapply similarly for light emitters and light detectors, as a personskilled knows, which is why the side of the light emitter is explainedas an example here for the sake of simplicity.

The light emitters described in this document emit the light withvarying intensity depending on the exit angle. It is important that mostof the inventive embodiments do not involve rotationally symmetricsystems, like the light emitters that are often known in the state ofthe art. Therefore, the directional characteristic preferably involves avalue dependent on 2 angles that characterises the strength of the lightemitted in the direction of this angle. For example, this can be aspecified percentage depending on the orientation angle on the plane ofthe light emitters and light detectors and the angle to a lineperpendicular to this plane, which runs through the emitters ordetectors.

The term directional characteristic is often used in the text in therelationship between light emitters and light detectors. In this case,the angle on the plane is advantageously specified such that 0 degreescorresponds to orientation towards the other respective components anddeviations from this direction are detected in the range of +/−180degrees.

It can be beneficial for a simplified representation to specify thedirectional characteristic of a light emitter to a light detector orvice versa purely as a function of the angle to a line perpendicular tothe emitter-detector plane through the component in the direction of therespective partner component. Simplified even more, this can be referredto as a steep or flat directional characteristic towards a correspondingpartner component. Flat means, in particular, that a relatively largeamount of light is emitted such that it reaches the partner componentwithout passing through deeper layers of the sample. Steep means, inparticular, that a relatively large amount of light is emitted such thatit must pass through deeper layers of the sample in order to reach thedetector. Emitters and detectors are preferably interchangeable in thisdescription. In addition the directional characteristic of a pair oflight emitter and light detector can be defined as the directionalcharacteristics of emitter and detector.

Non-transparent elements that shade the light, such as plastic or metal,can be used as means for producing a directional characteristic. Inparticular, they can be black or contain black pigment in order toabsorb the light. Furthermore, elements that reflect light can be used.They can be reflective or diffusely reflecting surfaces. In particular,they can also be coloured in order to create different directionalcharacteristics for different colours. The surfaces can also be curved.In addition, transparent materials can be used to conduct light. Thesecan be transparent plastics or glasses, in particular. They can alsoinclude dyes or colour pigments. In particular, the directionalcharacteristic can be influenced with the introduction of elements orpowders that scatter the light. Such elements can, for instance, beglass spheres, colour pigments, white pigments, white or coloured powderor paste, or air bubbles. In addition, the directional characteristiccan be influenced by the delimiting surfaces of various materials andparticularly by the shape of such surfaces or the surface properties.Examples of feasible delimiting surfaces in this connection would bebetween gas and glass, gas and plastic or glass and plastic, as well asdifferent glasses or plastics. In particular, the directionalcharacteristic can be influenced by lenses, diffraction grating, Fresnellenses, thin layers, prisms, or diffusion panes. The directionalcharacteristic can also be influenced by light conductors. In addition,the directional characteristic can be influenced by the shape, size, andorientation of the emitter and/or detector. This is also possible withthe shape and orientation of the semiconductor, in particular. This isalso possible with a casting of the semiconductor, in particular. Thisis also possible with the positioning of the semiconductor relative totransparent and non-transparent material elements, in particular.

In an advantageous configuration, the non-transparent materials are alsoused to ensure that only light from the emitter that has passed throughthe sample reaches the detector. Preference is given to a variant inwhich the non-transparent material forms a blocking element for thelight and thus blocks the path from the emitter to the detector. In anadvantageous variant, at least 50%, preferably at least 95% and ideallyevery path is blocked, in which the light must at least not pass throughthe sample, preferably at least a defined minimum path must pass throughthe sample. In an advantageous configuration, this minimum path is atleast 2% of the distance from emitter to detector, preferably at least20%, more preferably at least 50% and ideally at least 80%. In anadvantageous variant, this requirement is partly realised with thearrangement. In an advantageous variant, this requirement is partlyrealised with the evaluation process. In an advantageous variant, it isassumed for the calculation that the light that passes through thedelimiting surface of the sample and device more than 2 times is notconsidered.

In an advantageous variant, there is at least one pairing of lightemitter and light detectors in which light must not pass through thesample and is reflected at least partially on the sample surface on thepath from the light emitter to the light detector.

A group of similar pairs or a group of equal pairs or group of equaloptical paths between emitter and detector in connection with thisdocument should be understood as follows. A measurement can be conductedfor every possible combination of emitter and detector. This takes placewith activation of the emitter and emission of radiation. Preference isgiven to a configuration in which only one emitter is activated at atime. Preference is given to variants in which different emitters areactivated in succession. The emitted radiation runs through the sampleand at least partly reaches a detector. Preference is given to a versionin which multiple detectors are activated simultaneously. The signaldetected by a detector is the measurement value of the emitter-detectorpair from the activated emitter and the detector used of themeasurement. By varying the emitters and detectors, a multitude of suchmeasurement values is produced. These measurements preferably identifiedas a group under certain conditions. Different group formation rulesdepending on the configuration of the arrangement are also possible evenif only an approximately equal wavelength characteristic andapproximately equal distance are explicitly specified in thedescription.

For this purpose, for instance, the wavelength characteristic of theemitter of an emitter-detector pair must not match that of another foran equal wavelength characteristic. It is sufficient, preferably if thejointly created wavelength characteristic of the emitter and detectorsufficiently matches that of the comparable emitter-detector pair. Thismatch can also be limited to specific wavelength ranges that arerelevant for the analysis.

The exact same distance must not be observed for an equal distancecharacteristic. It is important that the volume of the sample throughwhich the photons arriving at the detector have passed is sufficientlysimilar between the pairs. The directional characteristic also has aninfluence on this. The emitter and detector distance essentiallydetermine how deep the light that is measured in the means penetratesinto the sample. The directional characteristic also has an influence onthis. Pairs that are sorted into a group of comparable or equal pairscan have a sufficiently similar emitter-detector distance andsufficiently similar directional characteristic with respect to theemitter-detector pairing, or the differences in directionalcharacteristic and distance can compensate each other such that asufficient comparability arises as a result.

In some cases, it is advantages to additionally require a comparableorientation for membership in a group of equal pairs.

Depending on the sample, analyte and measurement arrangement, one ormultiple or combinations of the aforementioned conditions in combinationwith each other or with other conditions are advantageous.

The term sample in connection with this document should be generallyunderstood as an object to be examined. This should, in particular, notpreclude the sample involving a living being or human. In particular,both living and non-living or no longer living objects to be examinedare meant by this term. Samples can have different states. Inparticular, solid, liquid and gaseous samples are possible. Examples fora sample would be: the ball of the thumb of a person, including the skinlayer, a blood, urine or tissue sample. A piece of fruit, a piece ofplastic, a pellet of powder (tablet), an exhaust gas sample or a pureedquantity of vegetable are also examples for a sample.

The concentration of an analyte in connection with this document shouldbe understood as a property of the sample to be examined. An especiallytypical property can be characterised by the concentration of asubstance in the sample. Examples of such substances include flavonoids,cytochrome C oxidase, glucose, HbA1c, fructose, advanced glycation endproducts (AGE), haemoglobin, carboxyhaemoglobin, methaemoglobin,synovitis, lactate, cholesterol. The analytes that are not recogniseddirectly, but indirectly in relationships with other substances are alsomeant in the scope of the document. This includes, for instance,recognition with cleavage products, waste products, marker substances,in the creation or breakdown of involved products. This also applies toinformation that can be determined from combinations e.g., of differentsubstances. In addition, the definition also comprises properties thatgo beyond the purely chemical concentration, such as microcirculation ofthe vessel, skin moisture, water content of skin/tissue, blood alcohol,drugs, tenderness of flesh, resistance of plants to frost, degree ofripeness of plants, NO2, pulse, oxygen saturation and heart frequency.Concentrations of an analyte are therefore also to be understood asconcentrations of substances in a part of the sample, in particular. Forinstance, the sample can be the living hand of a living person. Theinteresting part of the sample in this example is the blood of theperson. The interesting concentration is the alcohol in the blood. Alocal limitation is also meant. An example would be the concentration,e.g., moisture of specific substances in specific skin layers, such asthe epidermis or a depth of 0-0.5 mm. In particular, concentrationdistribution features are also meant, which, for instance, can begradients or graduations or oriented or non-oriented or isotropic oranisotropic. This also applies to the progression of concentrations overtime that can be, for instance uniformly, periodically rising orfalling. Therefore, the concentration of an analyte should also beunderstood as variables derived from one or multiple propertiesdescribed above. An example of a period concentration progression and avariable derived thereof is the determination of the heart frequencythat can be determined from the periodicity of the concentrationdistribution of specific blood substances in a body part, as well as theapproximate value for the general condition of the health of theanalysed person that can be deduced from this and other variables.

Emitters in the scope of this document should be understood, inparticular, as elements that emit the light or electromagneticradiation. This includes, in particular, ultraviolet radiation, infraredradiation, x-radiation and microwaves as well as radio waves and thefrequency ranges in between.

Examples include, in particular, incandescent lamps, glow lamps, lightemitting semiconductors, light emitting diodes (LEDs), light emittingconductors, lasers, laser diodes, fluorescent tubes, OLEDs, RGB LEDs,tubes, antennae, luminescent substances, flames, electric arc, sparksand additional sources of radiation known to a person skilled in theart.

Detectors should be understood, in particular, as elements that detectthe radiation emitted by the emitters and can convert the radiation intoa signal.

Examples include, in particular, phototransistors, photodiodes,photomultipliers, spectrometers, photoresistors, solar cells, tubes,camera chips, CCD cameras, semiconductors, LEDs, antennae, light fieldsensors, pyrometers and radiation sensors.

Transparent material should be understood, in particular, as materialsthrough which at least part, preferably the majority, of the radiationemitted by the emitters can pass through.

Examples are clear plastic or glass, milky or cloudy plastic or glass,coloured plastic or glass, transparent materials, gas, and plasticthrough which radio waves can pass.

Non-transparent material should be understood, in particular, asmaterials which prevent, at least in part, the radiation generated bythe emitters from passing through. This can, for instance, take place bymeans of absorption, reflection, interruption, or dispersion.

Examples include plastic or glass with black or coloured pigments,metal, ceramic, wood, conductive plastic, e.g., with radio waves.

Elements with volume percentages or surfaces that can be transparent ornon-transparent are also considered as a whole as transparent ornon-transparent material. Examples are a glass element that has beencovered by a non-transparent metal layer or lacquer layer or a metalelement that has been provided with holes in order to allow light topass through.

The definitions of transparent and non-transparent material can overlap.In such cases, the material that is rather permeable for the radiationfor the considered wavelength characteristic applies as the transparentmaterial and the material that is rather impermeable applies as thenon-transparent. In particular, the classification of a material candepend on the wavelength of the radiation. Transitions betweentransparent and non-transparent material do not need to be severe. Forthe purpose of simplification, the facts are preferably explained forsevere transitions without limitation on generality. However, thetransparency of a material can be influenced, for instance, withincorporation of pigments or chemical or physical reactions in somelocations. Examples are the development of photographic film, theincorporation of pigments on parts of an otherwise homogeneous plasticlayer or the incorporation of light-dispersing bubbles in a homogeneoustransparent member by a laser.

FIG. 1 Simple Emitter-Detector Arrangement

FIG. 1 shows a simple emitter-detector arrangement in which emitter 1and multiple optical detectors 2 are arranged side-by-side and arearranged in a line.

With this arrangement, the light back-scattered from the sample isdetected in three different locations. In the process, the distance tothe emitter increases. Optical paths 3.10 to 3.30 differ considerably.3.10 identifies a short optical path, 3.20 identifies a medium-lengthoptical path and 3.30 identifies a long optical path.

In order to be able to detect the inhomogeneity of a biological sample,such as the skin, multiple measurements are necessary in different skinlocations with this arrangement. This simple emitter-detectorarrangement necessitates additional measuring processes that must beperformed in succession and the measurement result can also beinfluenced by physiological changes between the measurements.

If the emitter-detector arrangement is arranged repeatedly in a deviceside-by-side as a solution to the problem, the effort is increased bythe same factor that the number of measurement points is increased. Itis a further disadvantage that the measurement points in the directionof their longest dimension cannot be positioned very closely to eachother.

FIG. 2 Emitter-Detector Arrangement in the Form of a Matrix

The disadvantages of the arrangement shown in FIG. 1 are solvedaccording to the invention with a two-dimensional emitter-detectorarrangement. FIG. 2 shows an example of such an arrangement.

A larger number of different optical path lengths arises in anadvantageous manner. Therefore, 3.10 shows a short optical path, 3.15shows a short to medium-length optical path, 3.21 shows an additionalmedium-length optical path and 3.30 shows a long optical path. In thearrangement in the form of a matrix, it is possible to achieve thenumber of measuring paths necessary with a smaller number of Emitters 1and optical Detectors 2 than a duplication of the arrangement from FIG.1 would have produced.

FIG. 3 Emitter-Detector Arrangement in the Form of aMatrix—Representation of 24 Short Optical Paths

FIG. 4 Emitter-Detector Arrangement in the Form of aMatrix—Representation of 16 Short to Medium-Length Optical Paths

FIG. 5 Emitter-detector arrangement in the form of amatrix—representation of 32 Different Medium-Length Optical Paths

FIG. 6 Emitter-detector arrangement in the form of amatrix—representation of 12 Long Optical Paths

FIGS. 3 to 6 show how the number of optical paths from Emitter 1 tooptical Detector 2 multiply heavily in the example arrangement while thenumber of Emitters 1 and optical Detectors 2 required for this purposeincrease less drastically. The various optical path lengths (3.10, 3.15,3.21 and 3.30) are shown in FIGS. 3 to 6 together with their frequencyof occurrence. The sum of at least the 84 optical paths shown in thefigures is produced with only 9 emitters and 14 optical detectors.

FIG. 3 shows the number of short optical paths 3.10 that is provided 24times with this arrangement. FIG. 4 shows the 16 short to medium-lengthoptical paths 3.15. FIG. 5 shows the 32 other medium-length opticalpaths 3.21 and FIG. 6 shows the 12 long optical paths 3.30.

FIG. 7 Example Cross-Section of a Device Housing

FIG. 7 shows an example housing for a device for the measurement ofanalytes on the ball of the thumb of the hand. This can be preferablyused for measurement of carotenoids. Housing 12 is shownconventionalised in a cross-section. To conduct the measurement, it isapplied directly on the ball of the thumb (see FIG. 8 ). The housing hasa curvature 7 with respect to the shape of the ball of the thumb.

Curvature 7 and bulge 8 contribute in an advantageous way to preventscratching of the optoelectronics 4 if the measuring device is, forinstance, placed on a table and moved back and forth betweenmeasurements. Curvature 7 and a surrounding or punctual bulge 8simultaneously contribute to a shielding of the optoelectronics fromexternal light during the measurement.

The optoelectronics 4 are preferably located in the centre of curvature7. Depending on the implementation, there can be a lateral offsetbetween housing 12 and optoelectronics 4. The optoelectronics areconnected to printed circuit board 6, which can help to receive andprocess signals.

A casting compound 5 is integrated between housing 12 andoptoelectronics 4 as a seal to prevent the penetration of moisture anddust. Preference is given to a housing design for a handheld measuringdevice that is chamfered over handle 11 and can be held during themeasurement.

In an advantageous variant of the device, the start of the measurementis triggered by pressing activation button 10. Activation button 10 isadvantageously arranged recessed in activation recess 9 such thatundesired switching-on is prevented.

As FIG. 7 shows, the activation button is preferably arranged such itcan suggest the position of the optoelectronics. A relatively preciseapplication of the measuring device on the ball of the thumb of the handis thus made easy as a result. In an advantageous variant, theoptoelectronics are also used to check whether contact has beenestablished with the test subject. A measurement is only triggered ifthis contact has been established.

In an advantageous variant, activation button 10 only reacts once acertain pressure has been applied. As a result, it can be ensured thatthe measurement is not started until the device is sufficiently pressedon the test subject.

FIG. 8 Housing with Positioning Aids for Measurement on the Ball of theThumb of the Hand

FIG. 8 shows an example of a device having housing 12 that is appliedwith handle 11 on the ball of the thumb 14 for the measurement. Themeasurement is started by pressing activation button 10. The device haspositioning aids that support the repeat accuracy for application of theoptoelectronics 4 on the ball of the thumb 14 of the hand 13. Thelateral guide 15 ensures the reproducibility of the measurement positionin one direction and guide 16 ensures the reproducibility in the otherdirection. In an advantageous variant of the invention the guides areadjustable such that they can be adapted to the user or the object to bemeasured.

In another advantageous variant, the stops are arranged such that theyare well-suited for different measurement object sizes withoutadjustment.

In another variant the guides are exchangeable or can be attached on thehousing of the device.

In an advantageous variant, tailored guide elements can also be used forthe specific user. For instance, an impression of a hand can be made ina curable plastic composition.

FIG. 9 Housing with Positioning Aids for Targeted Movement of the Deviceon the Surface of the Measurement Object

The positioning aids 15 and 16 of the example housing 12 described inFIG. 9 can also be used to purposefully move the optoelectronics 4 overthe surface of the ball of the thumb 14 of the hand 13 in order todetect the inhomogeneity of the measurement object as precisely aspossible. In an advantageous variant of the invention, it enablesreproducible movement along a track 18. In the process, eithercontinuous measurement values can be taken after pressing activationbutton 10 or measurement values can be detected at specific points ofthe measuring track 18. For this purpose, for instance, the depth guideelement 16 can slide continuously or incrementally along, for instance,a sliding path 17. The measuring track and sliding path can represent astraight line or a curve in the three-dimensional space.

In an advantageous variant it is also possible to use multiple measuringtracks. This can be achieved, for instance, by adjusting additionalguide elements.

The data recorded during the movement of the optoelectronics 4 can beoffset with a rule such that a representative value of the inhomogeneityof the measurement object is determined.

FIG. 10 Example Configuration of the Device

FIG. 10 shows an example configuration of the inventive configuration ofthe device. The optoelectronic components can be arranged on a carriermaterial or a printed circuit board 101. Emitters 102 and opticalemitter chips 104, as well as the optical detectors 103 are distributedon the carrier material 101 according to the inventive configuration.Detector chips are not shown in the simplified representation.Similarly, not all emitter chips are identified. Moreover, only someoptical emitters and detectors are explicitly identified as such withnumbers. The components that are not identified are also emitters ordetectors. For measurement of additional parameters, the arrangement hasa temperature sensor 160 and a moisture sensor 161 such that themeasuring conditions are detected very well and can be taken intoconsideration in determining the concentration of the analyte. The lightbarrier 107 consists of a material that is impermeable to light and isshown in the form of an exploded drawing at a distance from the devicefor better clarity. In the version of the device that is ready foroperation, the light barrier 107 is arranged on a printed circuit board101. The size and shape of the individual cavities have been selected inconsideration of the component volume and the orientation of theemitters and detectors, such that desired radiation and detectioncharacteristics are achieved and the light is preferably propagated toappropriate optical paths. If the light barrier, which is not shown inthis example, is produced as a separate component, it can be retrofittedon the arrangement of the optoelectronics and the cavities are cast witha material that is permeable to light. The transparent material is notrepresented in the drawing. Partially there are cavities that haveemitters or detectors that have one wavelength characteristic. Partiallythere are cavities that have emitters or detectors having more than onewavelength characteristic, such as RGB emitters or RGB detectors ormultiple single emitters and/or detectors.

FIG. 10 a shows an example arrangement of emitters and detectors thatcan be selected for the mechanical arrangement from FIG. 10 .

Emitters are identified with the letters a to y. Emitters having thesame letters have the same wavelength characteristic.

Emitters h, g, and i are not separated by non-transparent material.

Emitters x and y are example emitters that can have multiple wavelengthcharacteristics. They can emit light varying in wavelength.

Emitters y radiate light having a different directional characteristicthan emitters x.

The detectors are identified with the Greek letters α, β and γ.

Detector a has, for example, five different wavelength characteristics.

Detectors β and γ have different wavelength characteristics. With therectangular geometry, the directional characteristic is not rotationallysymmetrical.

FIG. 10 b shows an example group of equal emitter-detector pairs.

In this example, an approximately equal wavelength, approximately equaloptical paths and comparable directional characteristics were selectedas a feature for group membership. Four different orientations of theconnecting line from the emitter to the detector are recognisable, suchthat one optical path is realised in each 90-degree angle range.

FIG. 10 c shows an example group of equal emitter-detector pairs.

In this example, an approximately equal wavelength, approximately equaloptical paths and comparable directional characteristics were selectedas a feature for group membership. Eight different orientations of theconnecting line from the emitter to the detector are recognisable. It isrecognisable that a finer gradation of orientations take place incomparison with FIG. 10 b.

FIG. 10 d shows an example group of equal emitter-detector pairs.

In this example, an approximately equal wavelength and approximatelyequal optical paths were selected as a feature for group membership.Forty optical paths from the emitter to the detector are recognisable.It is recognisable that, in consideration of the orientation, thearrangement was selected such that little overlap could be achieved. The16 emitter-detector pairings with the middle detector analyse an annulararea around the central point of the device, wherein the orientation ofthe measurement is oriented towards this centre in each case. Theremaining 24 pairings that are shown also cover this annular area buthave an orientation that essentially runs transversely to the 16initially mentioned pairs. The multiple use of emitters and detectors isalso easily recognisable in this example. A sharp increase in the numberof possible emitter-detector pairings is achieved specifically with theuse of longer distances, which are made possible with an evaluationcircuit having higher dynamics. The connecting lines of emitter-detectorpairs are shown with different broken lines in FIG. 10 d . This shouldprovide an example that groups of equal emitter-detector pairs can alsobe divided into sub-groups. In general, the measurements of anemitter-detector pair can, of course, also be included in more than onegroup.

FIG. 10 e shows an example group of equal emitter-detector pairs.

In this example, an approximately equal wavelength, approximately equaloptical paths, and comparable directional characteristics were selectedas a feature for group membership. Three different orientations of theconnecting line from the emitter to the detector are recognisable. Threedifferent measurement locations are recognisable. This is an exampledemonstrating that the arrangements do not have to be symmetrical.

FIG. 10 f shows an example group of equal emitter-detector pairs. Inthis example, an approximately equal wavelength, approximately equaloptical paths, and comparable orientation were selected as a feature forgroup membership.

FIG. 11 Description of Electronic Components—Optical Emitters

For the evaluation of the measurement conducted with optoelectronicdevice 4, the emitter side of which is shown in this figure, it isadvantageous to activate the various optical emitters 1 in succession inorder to be able to detect the measurement data of the various opticalpaths. In particular, if only one light source is simultaneouslyactivated, a matrix arrangement such as the arrangement shown in FIG. 11offers unexpected advantages in the control. It is known from matrixarrangements that fewer control lines from control electronics 60 arerequired.

In the case of the described arrangement of optoelectronics, however,there is an unexpected advantage with the wiring, because thearrangement in the form of a matrix requires less conductor track spaceand optical elements 1 and 2 can thus be packed together more denselyand provide better measurement results.

The example shown in FIG. 11 is arranged such that 0 V is emitted ateach of LED line signals 21 to 26 with the exception of one line signalwhich is on a positive level. The column signals 31 to 35 are all on apositive level, with the exception of one signal which is at 0 V.

The light source at the point of intersection of the line signal on apositive level and the column signal at 0 V illuminates.

FIG. 12 Description of Electronic Components—Optical Detector EvaluationCircuit

FIG. 12 shows an evaluation circuit of optoelectronic device 4 withdifferent circuit variants.

In an advantageous variant, the evaluation of the light-sensitivedetectors 2 or other optical emitters 1 used in the system are organisedin the form of a matrix. In the process, multiple optical detectors canbe connected to a selection line 42 or 43.

In an advantageous variant, the transistors connected to selection line42 are spatially integrated in the matrix. In an especially advantageousvariant, they are arranged on the back side of the printed circuit board(on the side on which there are not optical components).

In an alternative variant, diodes are used instead of transistors, asshown by conductor 43.

The analogue signals of multiple optical detectors can be collected andmeasured on a common conductor 54, 55, and 56. In an advantageousvariant, the measurement can be carried out by measuring the duration oftime of the charge- or discharge-process of a capacity.

In an especially advantageous variant, the charge/discharge time isconfigured for a plurality of half of the mains frequency period. Mostlight-emitting means generate light in a frequency that corresponds todouble the mains frequency. If the measurement with a mains frequency of50 Hz is a multiple of 10 ms, interfering influences by a flickeringmains-operated light are minimised.

In an advantageous variant, the discharge takes place over a time spanthat is at least approximately balanced with the periodicity of possiblyexisting artificial light. Therefore, in locations with 50 HZ ACcurrent, for instance, the time span can be a multiple of 10 ms, becauseboth half waves of the mains voltage typically generate a light pulse.The same applies for locations with 60 Hz. With selection of the timespan near a suitable multiple of both frequencies, a system that can beused worldwide is provided.

In an especially advantageous variant, the described circuit can beconnected directly to a microcontroller. It can carry out the completefunction of the control electronics 60 in an especially advantageousvariant.

For this purpose, the LED line signals 21 to 26 and LED column signals31 to 35 are connected to digital 10 ports of the controller. The sameapplies for the detector line signals.

The controller now generates these signals such that exactly one LED isactivated, and one group of optical detectors is activated.

Then lines 51 to 56 can be connected to, for instance, positivepotential via an activatable resistor in the controller. With an ADconverter integrated in the controller, a rough value of the current canbe determined by the optical detector.

By setting conductors 51 to 56 to positive potential without resistance,the capacitor can be set to a defined potential.

Alternatively or additionally, the potential on the capacitor can bemeasured via AD converter or DA converter and comparators.

If conductors 51 to 56 are then switched to high-resistance potential,the change in voltage at the capacitor can be determined by means of anAD converter or comparator or when a threshold of a digital input iscrossed. The current through the detector can be concluded withmeasurement of the time required for this process.

By setting the threshold for the comparator, the time can be adjusted tothe beneficial charge times described above. If the charge time isshorter, one or multiple additional measurements can be conducted,wherein the results of the measurements can then be averaged in order toobtain a result that is not significantly influenced by flickeringartificial light.

In an advantageous artificial variant, each detector is evaluatedindividually, which provides the advantage of a quicker measurement.This is shown with detector inputs 51, 52 and 53.

FIG. 13 Description of a Device 1

FIG. 13 shows a part of a cross section of the device.

Optoelectronic components are installed on the carrier material 101,such as FR4 or ceramics, e.g., in the form of soldered SMD components.These components include optical emitters 102 (e.g., LEDs) and opticaldetectors 103.

The optical emitters 102 have one or multiple chips 104 that emit thelight. This light is received by the optical detector chip 105.

Transparent material 106 is used in order for the light to be able toreach the detectors from the emitters. This material may be plastic, forexample.

In order to ensure that the light cannot reach the detector directlyfrom the emitter and must pass through the sample to be measured,non-transparent material 107 can be used.

However, it may be advantageous if detectors and emitters are notseparated by a non-transparent material. For example, light reflected onthe surface of the sample can be analysed in this manner.

In many cases, it is important to influence the paths the light passesthrough the sample to be analysed. For this purpose, for instance, theorientation of the emitter chips 104 or detector chips 105 can beadjusted. The figure, for example, shows a vertical orientation of theemitter chip 104 to the right.

FIG. 14 Description of a Device 2

FIG. 14 shows an example implementation of the device with applicationof a sample 108 to be measured.

The sample to be measured in this example is a piece of human skin. Ithas 3 layers. The external layer 109, a middle layer 110 further towardsthe interior of the body and an even deeper layer 111.

These layers have different properties. With an optical measurement, theconcentrations of analytes in the various layers should be measured orestimated.

With the various distances of emitter chips 104 to the detector chip105, different optical paths arise, as is shown with optical paths 113and 114.

The optical paths shown in the image each represent only one type ofoptical path. In reality, the stream of light arriving at the detectoris comprised of a plurality of different paths having different lengthsand occurring with different probability. The paths are shaped byrefraction, diffusion, absorption, and reflection of the light in thetissue.

The quantity of light for the relevant optical paths is detected, thatreaches the detector from the emitter. The properties of the sample atdifferent depths can be concluded by comparing the measurement resultsof different optical paths. In this manner, properties of differentlayers, e.g., different skin layers, can also be concluded.

The measurements can be repeated at the same or different locations inorder to increase measurement accuracy.

For calculation of the concentrations of analytes at a specific locationin the sample, the measurement results are, for instance, weightedlinearly or non-linearly and then added together or linked in adifferent manner. The result is then weighted linearly or non-linearly.The weighting factors or weighting functions are selected appropriatelyin order to determine the desired concentration value in the desiredsample location.

It may be the case that the distances between detectors and emitterscannot be made short enough in order to generate optical paths fromwhich only a small part leaves the outer-most layer.

In other measurement situations, it is also desirable to influence theoptical paths such that a light path that is beneficial for the resultis provided. The example of a measurement for the exterior layer 109should not limit the general case in this here.

The invention shows multiple ways of solving this problem.

In FIG. 14 , light radiated from the emitter 104 furthest to the rightpasses especially flatly through the sample. This is marked as opticalpath 112. The flat optical path is achieved with the orientation of theemitter chip.

The position of the emitter chip also plays an important role. Opticalpath 115 shows an alternative position that produces a different opticalpath.

Of course, the orientation of the detector chip can additionally oralternatively be changed.

FIG. 15 Description of a Device 3

FIG. 15 shows a different device. With this device elements 116 areused, which can purposefully influence the reception and/or emissioncharacteristic and/or directional characteristic of emitter chip 104 anddetector chip 105.

These elements can, for instance, consist of materials that arepermeable 118 and impermeable 117 to light. When the materials that areimpermeable to light act as a diaphragm, they can influence thedirectional characteristic.

In addition, the directional characteristic can be influenced when thelight is interrupted, reflected, or refracted.

The surface of the element for optimisation of the directionalcharacteristic does not necessarily have to be level. In particular, thedirectional characteristic can also be influenced by lenses, grids orcurved surfaces or mirrors.

Optical paths 121 and 122 show that light can also reach the detector105 from the emitter 104 along multiple paths.

Optical path 123 shows that especially deep measuring paths can beachieved with purposeful orientation of the light beam away from theoptical partner and thus enabling passage through the layers 109, 110,111 of the sample. An orientation of the light beam vertically intosample also results in deep optical paths.

Optical path 120 shows that especially flat optical paths can beachieved with a suitable orientation of the directional characteristictowards the optical partner and that the light only passes through asmaller part of the layer 109.

FIG. 16 Device with Multiple Arrays

FIG. 16 shows an advantageous variant of the device.

In this variant, multiple emitter-detector arrays are used. Arrays 140and 141 are shown as an example.

The depicted arrangement is an example. Generally, more than 2emitter-detectors could also be used. The arrays do not necessarily haveto be flat and can also be curved. The array may also be a single curvedarray.

The arrangement can also be designed as variable, moving or adaptable tothe measurement. The example shows a simple linkage 143 with which thetwo housing parts 144 and 145 have a pivoting connection. However, themovement can also be achieved differently. In particular, the sample tobe measured 142 can be clamped or gripped with the movement. Therelative position of the housing parts 144 and 145 in relation to eachother can be detected by means of sensors, which facilitates theevaluation.

Optical paths that do not pass through the sample, such as 150, can beused to determine how the sample 142 is gripped.

Optical path 146 detects both parts of the tissue of the external layer109 and significant parts of the middle layer 110.

On the other hand, optical path 148 hardly detects any portions of themiddle layer 110. The properties of the middle layer can be determinedwell with a comparison of the two optical paths.

Optical path 147 shows a diagonal progression through the measurementobject. As a result, a longer optical path through the external layerscan be achieved.

The straight lines shown in FIG. 16 should not belie the fact that amajor portion of the light does not take the direct path but follows thedirectional characteristic of emitter and detector and a curve. Thedirectional characteristic in this arrangement can also be appropriatelyselected.

Optical path 149 shows that optical paths that do not run completely inthe sample to be measured can also be used.

FIG. 17 Especially Advantageous Variant of a Measuring Circuit

FIG. 17 shows an especially advantageous variant of the measuringcircuit.

This can be used for one or multiple phototransistors. For the purposeof simplification, it is only shown here with T1 and T2. The selectiontakes place again with selection signals 42 and 43. It is assured withthese signals that no current flows through the optical detector if itis not selected. Signals 42 and 43 can be switched to high resistancedirectly by the microcontroller 61 or they can also prevent the currentflow using additional components. For instance, this can take place viadiodes D1 and D2, which block the current flow with a suitable level at42, 43. Alternatively, other components can be used instead of thediodes, such as transistors. In addition, with the use of only onedetector per measuring input 56, the detector component can also beconnected directly to operating voltage such that D1 and D2 are omitted.

C1 is provided in an advantageous variant, which increases the naturalcapacity of detector and circuit. This capacity is charged anddischarged during the measurement.

In principle, the circuit can also be achieved with a reversed currentprofile. Charging and discharging are then interchanged. For the sake ofsimplicity, only one variant is described here.

The measuring cycle begins with the charging of C1 via output 56 or 57via R1 or R2.

In an advantageous variant, charging takes place via 57 and the voltagelevel is measured at C1 via 56. Especially high brightness can bedetected well in this step. This is identified below as Mode D. In theprocess R2 forms a voltage divider with T1, for example, such that thelevel of the current flow through T1 can be detected with measurement at56.

In an advantageous variant, 57 can be omitted, wherein 56 is usedsimultaneously or very quickly in succession for the charging andmeasurement.

In an advantageous variant, R1 or R2 can be omitted.

In an advantageous variant, R1 or R2 can be omitted if Mode D is notused. Alternatively, multiple microcontrollers offer an R1 and/or R2integrated in the controller.

In an advantageous variant, the current flow is measured repeatedly incycles during the measuring time in order to calculate the influence offlickering light source (e.g., with mains frequency), which can takeplace, for instance, by means of averaging.

Mode Z is used in an advantageous variant for high brightness. Thecapacity is initially charged in this mode. At the beginning of themeasuring time, 56 and 57 are switched to high resistance such that C1discharges via, e.g., T1. It is determined via 56 whether a specificdischarge threshold is reached. If yes, C1 is recharged via 56 or 57.This process is repeated cyclically during the measuring time. Thenumber of cycles and the overall time of the discharge are detected. Thecurrent circuit through the detector and thus the brightness can bedetermined by the number of cycles and the discharge required for thispurpose.

With very low brightness, Mode A is used. In the process, the voltage at56 is measured at the beginning of the measuring time and at the end ofthe measuring time. In order to increase precision, this can also takeplace repeatedly. The current flow through the detector element can beconcluded based on the voltage difference.

Mode M is established between Mode A and Mode Z. In this mode, multipledischarge cycles are carried out, like in Mode Z. However, the start andend voltage are measured in the same manner as in Mode A. With asuitable computation, the current flow can be determined more precisely.

In an advantageous variant, the voltage is not measured at the beginningof the discharge. It can also be estimated from the boundary conditionsof the discharge.

In a preferred variant, the end voltage is monitored by a comparator,which is typically integrated in a microcontroller.

The measurement of discharge times for measurement of current flow is aknown method. However, the combination of operating modes explained hereprovides the advantage that all modes are modified such that they coverthe same measuring time and average the measured signal over it. This isvery important and advantageous for the device described here for thesuppression of errors from flickering artificial light.

There are also special advantages due to the high dynamic range thatarises from the combination of measuring methods of Mode D, Mode Z, ModeM and Mode A. The high dynamic range permits detection of both veryshort optical paths and long optical paths with the same measuringcircuit. The circuit can also be applied to multiple detectors withoutmajor effort, such that a detector arrangement in the form of a matrixcan be realised.

It is also advantageous that no information about the brightness to beexpected is required at the beginning of the measurement. By comparison,methods working with the switchover of amplifiers have the disadvantageof having to initially measure in the most insensitive measuring range.Then, if the measured signal was low, a switch to a more sensitive rangetakes place and measurement takes place again. In the described detectorarrangement in the form of a matrix, this would be a major disadvantage,because the measuring time for determining flickering light has fixedlength and thus two or more measuring times are required. Therefore, themeasurement becomes significantly slower and only a lower number ofoptical paths can be measured in the total available measuring time. Theinventive design does not have this disadvantage. The brightness valueto be measured does not need to be known at the beginning of themeasurement. Measurements according to Mode D, Mode A, Mode Z and Mode Mall occur simultaneously. The correct mode can be selected dynamicallyfrom the data accumulated during the measurement without having torestart the measurement.

FIG. 17 a Measurement of an Optical Path

FIG. 17 a shows the process of the measurement of a light path. In anadvantageous application, a light source is activated, and themeasurement shown in FIG. 17 a is carried out for all detectors that donot share an input 56 (FIG. 17 ) simultaneously. Then the light sourceis deactivated, and the next light source is activated, and measurementtakes place again. If all light sources have been measured, thedetectors are switched via outputs 42, 43 (FIG. 17 ) and all lightsources are measured again. The sequence can also be different.

Each individual measurement proceeds as shown in FIG. 17 a . Thecapacity C1 is charged in an initial charging step 213. The voltage at56 is determined with an AD converter (FIG. 17 ). If this is at a lowlevel 207 a, Mode D is used. The voltage is measured cyclically duringthe time period of the beginning of measurement 201 to the end ofmeasurement 202 and the results are averaged. Curve 203 shows thevoltage progression with consistent brightness. Mode D is suitable forextremely bright situations.

If the voltage is high enough at time point 201, Mode A, Z or M, whichare subject to the same process, is used instead of Mode D. The chargevoltage 207 is stored. At the end of the measurement, the voltage 210 at56 (FIG. 17 ) is measured again and stored.

The difference between these voltages is the discharge voltage for ModeA, which has taken place in the time between 201 and 202. If thethreshold value 208 was never undercut during the measurement at 56(FIG. 17 ), Mode A is present. The corresponding curve is plotted as204. Low brightness values at the detector can be concluded directlyfrom this voltage. If necessary, a linearisation is applied. Mode A issuitable for very dark situations.

Curve 205 shows the voltage progression appears in Mode Z and Mode M.The voltage at C1 drops until the undercutting of threshold 208 isdetermined at 56 (FIG. 17 ). The time span 211 necessary for this isrecorded and charging is initiated, for instance via 56 or 57 (FIG. 17). After the charging is finished, a discharge is carried out again. Inthe process, the number of cycles is counted, the durations of discharge211 are measured and the discharge voltage strokes from 207 to 208 aredetected for the evaluation.

With a high number of cycles, the brightness at the detector isconcluded from the number of cycles alone or, in an advantageousvariant, from the number of cycles and the sum of discharge times 211.This is Mode Z. It is suitable for bright situations.

With a low number of cycles, e.g., in the range between 1 and 200cycles, Mode M is used. In this mode the level of the last cycle isdetermined with measurement of the voltage 210 at the end of measurement202 and establishing the difference from 207. The level of the lastcycle is added to the sum of the levels of the previous cycles. Thisvalue is related to the sum of the discharge times 211 plus thedischarge time 212. If necessary, a linearisation takes place before theformation of the sum. By these means, the brightness for medium-brightsituations is determined very precisely.

FIG. 18 a, b, c, d, e Directional Characteristic Caused by a RectangularArrangement

FIG. 18 shows an arrangement with a rectangular arrangement of the lightbarrier based on the example of optical emitter 1 in the centre of thedevice. The optical detectors 2 can be reached by the light viadifferent optical paths 3.40, 3.41, 3.42 having a different directionalcharacteristic.

Optical path 3.41 is represented in FIG. 18 b in a cross section alongthe optical path orientation shown in FIG. 18 . The broken lines showthe delimiting effect of the light barrier 117 on the exiting light andalso the partial shade region.

Optical path 3.40 is represented in FIG. 18 c in a cross-section alongthe optical path orientation shown in FIG. 18 . The broken lines showthe delimiting effect of the light barrier 117 on the exiting light andalso the partial shade region.

Optical path 3.42 is represented in FIG. 18 a in a section along theoptical path orientation shown in FIG. 18 . The broken lines show thedelimiting effect of the light barrier 117 on the exiting light and alsothe partial shade region.

In a comparison of FIGS. 18 b and 18 c , it can be seen that the lightexit angle in FIG. 18 c is lower and the transmission of light 3.40 intothe sample is steeper. Therefore, there is a lower percentage of lightavailable, which only passes through the tissue in the flat layers. Thisis achieved with a narrower arrangement of the side walls of therectangular shape.

In a comparison of FIGS. 18 b and 18 a , it can be seen that the lightexit angle 3.42 in FIG. 18 a is wider than 3.41 and the transmission oflight into the sample is booth steep and flat. Therefore, there is ahigher percentage of light available, which only passes through thetissue in the flat layers. This is partly achieved with a widerarrangement of the side walls of the rectangular shape. This is alsoachieved because the section through the emitter chip along thediagonals produces a greater width of the light-emitting surface. Thedirection-dependent variation in the emission characteristic can also beachieved with an annular shape of the light barrier by using an emitterchip which has corners.

With a comparison of signals having different directionalcharacteristics and with a comparison of signals having different pathlengths, the absorption and dispersion share can be calculated in twoways and thus be more precisely determined, and it is also possible todraw conclusions about tissue, which shows deviating absorption anddispersion behaviour in the layers of tissue at different depths.

FIG. 18 d shows the analysed volume region of optical path 3.42, whichalso includes portions of flat light. Line 3.42 a, which is drawnthrough, symbolises a boundary of the space through which asignificantly strong flow of photons passes. In fact, the likelihood ofthe presence of photons slowly decreasing outwards is more probable. Thefixed boundary is only provided to illustrate the relationships moreeasily. The region near the lower arc of 3.42 a is especially importantin this connection. The photon density is also especially high there.The relevant differences from FIG. 18 e are recognisable specifically inthis region.

This figure should also demonstrate the fact that the delineated region,with a high probability of presence of photons, is based on the emittedphotons, but based on only those photons that are emitted by the emitterand detected by the detector. These photons all take somewhat differentpaths. They pass through a volume region in the sample which mainlyextends above the connecting line between the emitter and detector.However, a lateral deviation from this connecting line will always occuras well. The volume region through which radiation occurs is called an“optical path” and is shown as 3.42 a in FIG. 18 d and its edge isrepresented with a line drawn through. Again, it shall be noted, thatthe region ends with a somewhat soft transition and thus has no fixededge. Somewhat banana-shaped volume regions which have a higher densityof photon presence often arise in the shorter path-length range fromemitter to detector.

In FIG. 18 e a directional characteristic having a narrower emissionangle is shown. The lower arc 3.40 a does not run as flatly as arc 3.42a from FIG. 18 d identified by the broken line. The influence of theflat tissue layers on the measuring signal is less in 3.40 a. With thecomparison of both signals, the influence of the flat and the deeperlayers are separable.

In order to prevent the mathematical methods used to separate thementioned influences from amplifying measurement errors or noise, themethod is combined with the use of multi redundant optical paths. Anexample of this is shown in a matrix shaped arrangement in FIG. 18 .

In an advantageous arrangement, both emitters and optical detectors canachieve the necessary directional characteristic.

Preference is given to a version in which the production-baseddifferences in the emission characteristic of the light source areoptimised by filing the emitter cavities with a diffuse material that ispermeable to light.

In an advantageous variant, the rectangular shape provides an especiallyspace-saving arrangement that can accommodate an especially large numberof light emitters and light detectors on a small surface.

In advantageous variant, the variation of the emission directionalcharacteristic depending on the emission direction is not or is not onlyachieved with the shape of the light barrier, rather at least partiallywith the shape and position of the emitter or detector itself. Examplesfor this include the selection of a rectangular emitter or anon-horizontal arrangement of the emitter surface.

FIG. 19 a, b, c, d Increase of Spectral Resolution with Combination ofDifferent Optical Emitters with Different Optical Detectors

In the present invention the spectral resolution of the arrangement isincreased by purposefully combining different light emitters withdifferent light detectors. This is shown in FIG. 19 a to d.

FIG. 19 a shows the relative spectra of the two emitters E1 and E2.According to the invention, wide-band emitters are also purposefullyused here. Wide-band emitters in an advantageous configuration arewell-suited for detection of general properties of the sample that arenot oriented towards a special substance. Narrow-band emitters are alsoused. In an advantageous variant, the narrow-band emitters are used fordetection of special substances. FIG. 19 b shows the relative spectra ofthe two detectors S1 and S3. It is recognisable that the spectrum fromE2 matches detector S3 well and E1 matches S1 well. In a known solutionvariant, two different wavelengths would be measured, because E2 wouldbe measured with S3 and E1 would be measured with S1. FIG. 19 c shows aninventive optimisation of the arrangement. In addition to the indicatedmeasuring paths K1:E1→S1 and K4:E2→453, the paths K3:E1→4S3 andK2:E2→4S1 are measured. The results are visualised in K1 to K4. Thecurves show the sensitivity of the measuring paths depending on thewavelength. With use of evaluation algorithms explained later in thisdocument, M1 and M2 are also obtained as results of mathematicaloperations between measurement results from K1 to K4. FIG. 19 d shows atable that lists the emphases of curves K1 to K4 and M1 to M2 sorted bywavelength. With the combination of the variation of wavelengthcharacteristics for light emitters and light detectors, a recognisablyfiner wavelength resolution has been achieved.

Advantageous Spectral Configuration

In an advantageous configuration, at least 3 different spectralcharacteristics are realised with the light emitters.

In an advantageous configuration, at least 2 or 3 different spectralcharacteristics are realised with the light detectors.

In an advantageous configuration, a larger number of usable wavelengthcharacteristics is yielded in a combination of light emitters and lightdetectors than there are emitters with different wavelengthcharacteristics and detectors with different wavelength characteristics.

In an advantageous configuration, a larger number of usable wavelengthcharacteristics than there are emitters with different wavelengthcharacteristics and then there are detectors with different wavelengthcharacteristics is yielded by using a combination of light emitters andlight detectors.

In advantageous variant, the number of usable wavelength combinationsincreases by connecting the detectors to a measuring circuit with anespecially high dynamic range.

In an advantageous configuration, combinations of emitters and detectorpairs arise, which, despite different spectral characteristics of thelight emitters in combination with the light detectors, result insimilar overall spectral characteristics like other pairings. Thesepairings are used in an advantageous variant in order to realise abetter variation of optical path orientations and optical paths lengths,as well as different measuring locations in accordance with the othersections of this description.

Advantageous Geometric Arrangement

In advantageous arrangements the light sources emit differentwavelengths.

The LED identified as LEDxx-yy below is the LED at the intersectionpoint of the row signal yy is identified with the column signal xx fromFIG. 11 .

The arrangement shown in the example is symmetrical and regular, which,however, is not a requirement. Advantageous arrangements can also beasymmetrical and irregular, because, for example, a larger number ofoptical path lengths can be achieved as a result.

If a wavelength is especially important, it can be applied to thepositions LED32-22, LED34-22, LED32-24, and LED24-34, because a largequantity of short optical paths is yielded as a result. In anadvantageous variant this or a comparable position is occupied by an LEDwith a wavelength at which the substance to be measured either reflectsor absorbs. In an alternative advantageous variant this or a comparableposition is occupied by an LED that permits an estimation of the generalabsorption and is not in a spectral range in which a substance to bemeasured absorbs or reflects.

In an advantageous arrangement, the emitters of the described wavelengthare positioned such that the shortest distance of an emitter in thisposition to the detectors occurs at least two times. In an advantageousalternative the shortest distances differ by less than 25% in theirlength. Alternatively, this can be 50% or 80%. In an especiallyadvantageous arrangement the optical paths of the light of thiswavelength differ in their orientation.

This applies similarly for arrangements in which emitters and detectorsare interchanged.

For certain wavelengths it is especially important to have especiallyshort paths through the object to be measured. This is due, in part, tothe fact that light of certain wavelengths is heavily absorbed in theskin, which is a frequent measuring object. This is also due to the factthat short path lengths measure primarily light portions that have notpenetrated deep into the object to be measured. If a determinationshould be made for substances that are primarily in these layers closeto the surface, characteristic wavelengths must be measured, ifnecessary, with short optical path lengths.

In advantageous variants, however, concentrations of deeper layers arealso identified in the measuring object by removing the influence of thelayers close to the surface. For this purpose, this influence must firstbe measured by means of measurements with a short optical path length.As an alternative to this, optical paths that have penetrated todifferent depths of the tissue due to different emission characteristicsare mathematically combined with each other.

The arrangement shown in the example has an especially short opticalpath length for LED31-22, for instance.

In an advantageous variant of the invention, emitters that emit in awavelength range for which detection with a short optical path length isadvantageous are arranged at positions having a short distance to thedetector. In an especially advantageous variant, emitters and detectorsare arranged immediately next to each other.

In an advantageous variant, LEDs with important wavelengths occupy morethan one position adjacent to the detector. In the example, this couldbe LED31-22, LED33-24, and LED35-22.

In an alternative advantageous variant, LEDs of various wavelengthsoccupy the directly adjacent positions in order to be able to conductmeasurements for many wavelengths with a short optical path. In theexample, LED33-23 could emit 670 nm, LED31-21 660 nm, LED33-24 650 nm,LED33-21 640 nm, LED33-22 630 nm and LED33-25 620 nm.

In an advantageous arrangement, the emitters are arranged around thedetectors such that the spatial arrangement in the surface allowsmultiple adjacent neighbours with short optical paths to a detector. Inan advantageous variant, the optical paths differ in their direction andorientation in an advantageous variant by at least 85°, in analternative variant by at least 40° and in another alternative variantby more than 20°, in a further alternative variant by more than 10° or5° or by more than the deviation based on production tolerances of aline arrangement.

This applies similarly for arrangements in which emitters and detectorsare interchanged. This text refers in part to an optical component thatcould be an emitter for light or a detector for light and its partner.The partner of an optical component is, with detectors, a component thatcan emit light and, with emitters, a component that can detect light.During the measurement, the light travels along the path between thecomponent and its partner, wherein the part of light that finds thispath is typically measured. A connecting line from a component to itspartner is to be understood as the line from the averaged emissionlocation of the light-emitting surface to the averaged detectionlocation of the light-sensitive surface. The distance of an opticalcomponent to its partner should be considered the length of this line ifthe distance between the housings is not meant.

In an especially advantageous arrangement, the concepts are combined.

For example, an especially important wavelength is positioned at thepositions LED31-22, LED33-22, LED35-22, LED31-24 LED33-24 and LED35-24,whereas the comparable positions LED31-23, LED33-25 and LED35-23 areoccupied by a somewhat less important wavelength which is, however,still important enough that redundant measurement is desired. The alsocomparable positions LED31-25 LED33-23 and LED35-25 are occupied by 3additional different wavelengths.

The number of optical path lengths for the respective wavelength can beadapted to the requirements of the measurement by using thetwo-dimensional arrangement.

According to the invention, an arrangement is used in which the opticalpaths arise as a combination of the positions of emitters and detectorsthat are arranged not just in a line or a recognisably close proximityof a line.

According to the invention, optical paths arise that are not paralleland have orientations that differ from each other by at least 3°, 10°,25° or 40° in an advantageous manner.

According to the invention, the arrangement produces optical paths withwhich the number of equal-length optical paths of a wavelength differsfrom the number of equal-length optical paths of another wavelength. Inthis connection, equal length should not be interpreted as only theexact equal length and should instead be interpreted such that it alsocovers acceptable differences in the scope of the measurement, whicharise, for instance due to production imprecisions or the minimumtechnically feasible distance of components to be positioned next toeach other.

In particular, equal length should be interpreted if the differences indistances are less than 30% or 20% or 10% of the maximum optical pathlength.

In particular, more than 2 nearly equal-length optical paths of awavelength arise in an advantageous variant.

In an advantageous variant, detectors and emitters are arranged suchthat the distribution of optical path lengths is different for thedifferent wavelengths. The result is wavelengths with a spatialresolution of optical path lengths in the range of paths that areshorter than the maximum distance having a finer path length resolutionthan optical paths with other wavelengths, with “maximum distance” beingdefined as a distance that is so long that using it makes limited sensedue to the long distance. In an advantageous variant, path lengthdistances for one wavelength are finer by a factor of less than 0.9 orin a more advantageous way, by a factor of less than 0.8 or by a factorof less than 0.6, or by a factor of less than 0.3 than with otherwavelengths.

In particular, in an advantageous arrangement, at least one optical pathdistance is yielded between two optical paths having the same wavelengththat is less than 100% of the detectors size, emitter size or thedistance of two components of these two categories. An especiallyadvantageous arrangement yields 50% of the detector size or, in an evenmore advantageous arrangement, 20%, 10% or even 5%.

In an advantageous variant, optical path lengths can be achieved withthe described arrangement that can differ by the following factors fromthe distances of detectors. In an advantageous variant, the optical pathlength differences of one wavelength are less than twice the detectordistance, in an especially advantageous variant less than the detectordistance and in an even more advantageous variant less than 55% of thedetector distance.

In an advantageous variant there are many fine graduations in theoptical path lengths for larger optical path lengths.

In a typical implementation of the invention the number of significantlydifferent optical path lengths is greater than the number of detectorsand greater than the number of emitters.

In a typical configuration of the invention the number of optical pathsis the product of the number of emitters and number of detectors.

In an advantageous configuration, not all optical paths of a wavelengthdiffer significantly in length.

In order to be able to better influence the penetration of the sample,multiple matrix-type sensor arrangements are used in an advantageousvariant of the invention. An example of such an arrangement is explainedin FIG. 16 and the corresponding figure description.

Emission Characteristic of the Emitters and Detection Characteristic ofthe Detectors

To detect the inhomogeneity of a sample, particularly if it isbiological tissue, the emission characteristic of the light into thesample and the detection characteristic of the measured light coming outof the sample play an important role. Since the light propagates in thesample in different optical paths depending on the irradiation angleregion, the optical path variance can be influenced by the number ofirradiation angle regions per light source. A higher variance providesbetter represents the inhomogeneity conditions of the sample.

It was determined in during examinations in a surprising way that anon-rotationally symmetric irradiation or deflection angle often resultsin a better consideration of the inhomogeneity of the sample and ahigher precision in determining the concentration of analyte.

In an advantageous version, at least two different preferred angleregions of irradiation at each irradiation location for each lightsource and at least two different preferred angle regions for thedetection angle at each detector for the detection of the light exitingthe sample are realised.

In an additional advantageous version, the realisation of differentpreferred angle regions takes place with the purposeful design of alight barrier that impedes the crosstalk of the light from the emitterto the detector. As a component, the light barrier completely shieldsthe emitters and detectors from each other after its application in anadvantageous variant. In an advantageous variant, emitters, anddetectors each have their own cavity with a purposefully tailoredgeometry.

Preference is given to a version in which the light barrier has ageometry with corners and an even more advantageous version has arectangular geometry. With a rectangular geometry, two vastly differentpreferred angle regions can be adjusted with an emission of photons inangles preferably from 5°-175° to the irradiation and detection surfacein an advantageous variant. The packing density of the emitter anddetector arrangement enclosed by the light barrier is higher with arectangular configuration according to the invention than with a roundgeometry of the light barrier.

FIG. 18 shows an arrangement with a rectangular arrangement of the lightbarrier based on the example of optical emitter 1 in the centre of thedevice. Further explanation and advantageous configurations for this canbe found in the figure description.

Design of the Light Barrier

Preference is given to a version in which the light tightness at thecontact point of the light barrier and printed circuit board of theemitters and detectors is achieved with purposeful heating of thecircuit board. A light barrier produced in plastic melts/softens in theregion of the contact surface and thus closes a possible gap between thecontact surface and light barrier. In an advantageous design, printedcircuit board tracks that enable a heating of the appropriate positionare arranged on the printed circuit board. An example of design is shownin FIG. 10 and explained in the corresponding figure description.

Preference is given to another solution in which the emitters anddetectors are first completely cast with a material that is impermeableto light and then thin slits are made (e.g., using a fine saw blade),which penetrate into the casting material to the bottom of theemitter-detector plane. The slits are then cast with a material that isimpermeable to light.

Description: FIG. 13 Description of a Device 1

FIGS. 13, 14 and 15 show examples of an advantageous configuration ofthe light barrier in a sectional view. Further explanations andadvantageous configurations can be found in the figure description.

Spectral Analysis of the Sample

In order to detect the substance to be detected, light of one ormultiple wavelengths that is absorbed or reflected by the substance isused. In some cases, the substance is also excited with a wavelength andthen the light of another wavelength is emitted, which is then detected.This can take place, for instance with luminescence and Ramanscattering, which can also be used for detection.

Since a multitude of substances is normally present in the sample, theinfluence of substances having an optical effect in the region of thewavelengths that are relevant for the substance to be analysed iscompensated for. For this purpose, additional wavelengths from whichcorrection values can be determined are used for the measurement. Thesecorrection values can have a direct relationship with the concentrationof one or multiple other substances, or they can be wavelengths that arelocated next to the wavelengths for detection of the substance and thatthey detect the optical characteristic of all substances in the samplenear the wavelength to be analysed. The algorithmic processing isdescribed in the chapter on the evaluation algorithm.

In the state of the art there are arrangements in which two or morewavelengths are measured. In the process, for instance, multiple lightemitters of different wavelength are used. Detectors that are optimisedfor the wavelength of the light emitter are used for each sort ofemitter.

In the present invention the spectral resolution of the arrangement isincreased by purposefully combining different emitters with differentdetectors.

This is shown in FIG. 19 a to d . The figure description includesinformation about the advantageous configuration and applicationprocesses, as well as example configurations.

In an advantageous configuration, combinations of emitters and detectorpairs arise, which, despite different spectral characteristics of thelight emitters in combination with the light detectors, result insimilar overall spectral characteristics like other pairings. Thesepairings are used in an advantageous variant in order to realise abetter variation of optical path orientations and optical paths lengths,as well as different measuring locations in accordance with the othersections of this description.

Evaluation Circuit

In order to be able to use numerous emitter-detector pairs for bettermeasuring precision and repeat accuracy, high dynamics of the detectorsare required, because both a large number and a low number of photonsare detectable and can be differentiated from the noise.

The invention results in high dynamics in an advantageous way such thata larger number of emitter-detector pairs for detection of inhomogeneityof the sample is available with the same number of emitters anddetectors. A reproducible measuring result can thus be obtained with alower number of components.

Advantageous Evaluation Circuit for the Detectors

In order to be able to connect the characteristically high number ofoptoelectronic components with low technical difficulty, various designsof the evaluation circuit are advantageous. Some examples of this areshown in FIG. 12 . Different variants are shown in FIG. 12 and in itsdescription. It is advantageous to use only one of these variants in anadvantageous configuration. The figure description explains examples andadvantageous variants.

In an advantageous variant, detectors that transmit data via a digitalinterface are used as components. In an advantageous variant this is abus system, such as I2C or SPI. In an advantageous configuration thisenables simpler wiring and higher packing density.

In an advantageous variant of the invention the measured light quantityis detected by the detectors, wherein capacities are charged anddischarged. Advantageous configurations and processes and exampleimplementations and processes are shown in FIG. 17 and explained in thefigure description.

It is advantageous in the configuration described in FIG. 17 that noinformation about the brightness to be expected is required at thebeginning of the measurement. By comparison, processes working with theswitchover of amplifiers have the disadvantage of having to be initiallymeasured in the most insensitive measuring range. Then a switch to a lowsignal in a more sensitive range takes place and measurement takes placeagain. In the described detector arrangement in the form of a matrix,this would be a major disadvantage, because the measuring time fordetermining flickering light has a fixed length and thus two or moremeasuring times are required. Therefore, the measurement becomessignificantly slower and only a lower number of optical paths can bemeasured in the total available measuring time. The inventive designdoes not have this disadvantage. The brightness value to be measureddoes not need to be known at the beginning of the measurement.Measurements according to the modes explained in the figure description(Mode D, Mode A, Mode Z and Mode M) all occur simultaneously. Thecorrect mode can be selected dynamically from the data accumulatingduring the measurement without having to restart the measurement. Thisis very advantageous, because with measurements on human skin theabsorption varies heavily due to different skin types or differentconcentrations of analyte. Since the light attenuation through the skinwith, for instance, skin type 5 is significantly greater than with skintype 1, the signal-noise ratio changes for the measurement. Depending onthese conditions, measurement in accordance with the invention takesplace in a mode that also enables exact determination of the analyte tobe measured with a greater emitter-detector distance. Therefore, avariation of the exposure times for improvement of the signal-noiseratio is not necessary with the inventive configuration of the measuringcircuit in an advantageous variant.

The described circuit variant can also be implemented in alternativevariants in which, for instance, charging and discharging processes areexchanged.

In an alternatively advantageous variant, a current is initiallyamplified by the detector and converted from analogue to digital in anadvantageous variant.

In an advantageous variant the brightness measurement is performedmultiple times in order to detect and/or compensate for fluctuations asthey occur, for instance, due to periodic or steady physiologicalchanges. Changes to the measurement and environmental conditions canalso be compensated for or purposefully utilised. An example is theundesired heating of the sensor during the measurement, the influence ofwhich can be better compensated for with repeated measurement. Theheating can also take place purposefully, for instance, in order shiftthe wavelength characteristic.

Process for More Precise Determination of Measurement Values with Use ofAdditional Information

In an especially advantageous variant of the invention, compensation forerrors of the device is achieved through detection of environmentalinfluences with additional sensors. In particular, the following sensorscan be used:

Temperature

Moisture of the sample on its surface, particularly the contact surfacefor the emitter-detector arrangement

Moisture of the sample interior (e.g., via high-frequency or capacitivemeasurements)

Air gaps between sample and emitter-detector arrangement (e.g., viacapacity measurement, application pressure measurement, triangulation)

Roughness of the sample surface (e.g., due to optical or capacitivesensors, e.g., fingerprint sensor)

Colour Abnormalities of the Sample Surface

Conductivity of the tissue of the user (various processes), pressureexerted with application of the arrangement on the sample, e.g., skin.

In an advantageous variant the information of these sensors and theoptical measurement values of the device are used to estimate themeasuring uncertainty or standard deviation. For this purpose, themeasurement values of past measurements and their time difference canalso be used. In particular, statistical information about measurementvalues and the distribution of the measurement values can also be used.

In an advantageous variant, the estimated measuring uncertainty orstandard deviation is used in order to determine the number ofmeasurements required to achieve a desired precision.

In an advantageous variant the result is shown to the end customer indiscretised values. This prevents the customer from drawing incorrectconclusions, e.g., about their health status, based on measurementfluctuations. In the process measurement results that, for instance,represent a concentration are assigned to categories.

The last result of this user (how the user is differentiated from otherusers is explained below) is incorporated into the decision regardingthe classification of the measurement result in a category in anadvantageous way. Therefore, the probability of changes visible for theuser over time that are due to measurement uncertainties can be reducedin an advantageous variant. In an advantageous variant, the visibility(or perception) of relevant changes of the measurement value for theuser is not significantly delayed by this method.

In an advantageous variant, one or multiple additional measurements canbe conducted if the measurement data or the history of measurement dataor other data indicates that the decision regarding which resultclassification should be shown to the user is influenced too heavily bymeasurement uncertainties. In an advantageous variant, for instance,additional measurements are conducted if the measurement results are inthe boundary region between two discrete output levels.

In an advantageous variant the indicated additional sensors can be usedin order to provide advantageous environmental conditions for themeasurement. For instance, temperature and moisture sensors can be usedin order to provide advantageous conditions for the measurement usingelements that can influence the parameters. For instance, the device orthe surface of the optoelectronics can be heated in order toreduce/prevent a temperature drift due to contact with the sample.Moisture can, for instance, be brought to an advantageous range by usingairflow that is blown through small openings in the surface of theemitter-detector arrangement. The distance of the sample to theemitter-detector arrangement can, for instance, be reduced by extractingthe air between the surface of the optical electronics and sample andthe sample is thereby practically aspirated. An unfavourable measurementlocation can be changed with a signal to the user to use a differentmeasurement location or by showing the quality of the measuring locationto the user.

Some of the known processes for improvement of the measuring situationare also applicable in an alternative variant without correspondingadditional sensors.

Calibration measurements on the respective skin conditions of a user cantake place by mechanically moving the device over the skin andpermanently generating measurement results with multiple emitters andreceivers in a matrix-like arrangement such that a 2 or 3-dimensionaltopography of measurement values over the desired measurement spacearises. With a subsequent measurement in which the device does notnecessarily have to be moved any more, the new measurement location canbe incorporated into the topographical image such that, for instance,the earlier determined carotenoid value can be compared with the newlydetermined carotenoid value. Changes can thus be identified moreprecisely and earlier, because with an inhomogeneous distribution of asubstance, such as the carotenoids, the corresponding localconcentrations can be compared with each other. Since each subsequentmeasurement usually does not take place in the same measurementlocation, the actual measured change is not directly communicated to theuser. It could be that the previous measurement has taken place in alocation with lower or higher concentration and the change is onlycaused by the new measurement location. The output of the newmeasurement value could cause the user to make incorrect assessments.The output measurement value can, thus be calculated, for instance, withreference to earlier measurements as an arithmetic means such that nonumerical change from earlier measurements arises for the user. With anadditional indicator in the form of an arrow that indicates the rising,falling or consistent tendency, however, the actually identified changein an advantageous variant is represented.

The precision of the change determination can still be improved in thatthe 2 or 3-D topography incorporates, for instance, the carotenoidconcentrations based on different depths of the skin. For instance,concentration gradients for carotenoids in the skin are known. If theconcentration determination in individual skin layers is carried outusing the known SRR method (f. U.S. Pat. No. 7,139,076 B1), it may bepossible that changes are not identified in all skin layers.

Therefore, the comparison can relate to specific skin layers havingconcentration level temporally or physiologically precedes a differentposition. Based on this knowledge, the user can derive furtherinformation that helps him trace a consciously or unconsciouslyinitiated change in a way of living (duration of sleep, nutrition, andalcohol consumption) to a specific action. The resulting learning effecthelps the user to act accordingly in the future, which can beadvantageous, for instance, in the sense of prevention (reduction of therisk of future illness).

Tracing measured concentrations to specific behaviours can also beimproved if information that the user provides in written answers in theform of a questionnaire is processed in addition to the pure skinmeasurements. This questionnaire can be evaluated as a 2-D or 3-Dtopography, wherein this topography is applied with local reference withthe 2-D or 3-D measurement topography described above by means of, forinstance, superimposing the two. In the process, peaks can meet valleysor peaks can meet peaks such that a specific relationship can bedetermined from this constellation.

Coupling

Preference is given to a design in which emitters are positioned aroundthe perimeter on the edge of the emitter-detector distribution. Thecomparison of measurement values enables the checking of the correctcoupling of the overall emitter-detector arrangement on the sample. Withmeasurements on the inner surface of the hand, it can be determinedwhether a flat emitter-detector arrangement is applied all around in thesame way based on the curvature of the ball of the thumb. Locallydifferent coupling conditions sustainably influence the measurementresult in specific applications.

It has been determined in a surprising way that by comparing thresholdvalues for the received light of emitter-detector pairs in which theemitter is arranged in the edge region and for pairs having the samedistance, in many applications it is possible to differentiate acomplete coupling of the emitter-detector arrangement from an incompletecoupling. In an advantageous configuration of the invention, thecoupling of the sample is measured and monitored. In an advantageousconfiguration this takes place by applying threshold values to the lightmeasured on selected optical paths.

The checking of the coupling takes place at the beginning of themeasuring procedure in an advantageous version. With incompletecoupling, the measurement is immediately interrupted in an advantageousvariant, which would spare unnecessary measuring time. The user isprompted to repeat the measurement by outputting a message.

In an alternative variant, repeat measurement does not take place. Theevaluation of the measurement can refrain from consideration of therelevant edge zone region such that only optical paths for which thecoupling was correct are factored in.

If the incomplete application of the emitter-detector arrangementresults in a regular light gap between the tissue surface andemitter-detector surface, which leads to a penetration of externallight, preference is given to a version in which the determination isachieved by measurement of the brightness value with the emitters of thedevice switched off.

However, the checking of the coupling does not only apply to theincomplete application of the emitter-detector arrangement on thesample; it also applies to changed coupling conditions due to partialmoisture or fatty formations on the skin surface, local soiling, pigmentdisturbances, injuries, scars, etc. Coupling problems become morerecognisable with more comparisons of equal optical paths and they canbe eliminated by disregarding the relevant partial measurements or by apurposefully repeated measurement. According to the invention,therefore, both the measurement accuracy and the repeat accuracy of themeasurement are improved.

Preference is given to a design in which moisture sensors applied on thesurface of the device, which is in contact with the sample for themeasurement, are used to check the moisture conditions on the samplesurface.

Temperature Drift of the Light Source

If LEDs are used as emitters, their optical spectrum shifts as theemitter heats up when the LED is activated. When measuring biologicaltissue, a shift takes place due to the body temperature with applicationof the device on the skin. As the temperature gradient becomes higher,the temperature drift also increases. With temperature control of theemitter-detector arrangement, the temperature gradient can be reduced.It was determined based on measurements that some additionally appliedconductors used as a heating element were sufficient in order toincrease the temperature on the plane of emitters and detectors at thestart of the measurement such that it corresponded to the human bodytemperature for in vivo measurements. It could thus be determined in asurprising way that the repeat accuracy of the measurement is improvedwith this measure.

Process for Calculation of Physiological Parameters or SubstanceConcentrations

The process is used to determine substance concentrations, such as thecarotenoid concentration in human skin or other samples. Alternatively,physiological parameters can also be determined, such as the degree towhich the skin is protected from ageing or solar radiation.

In particular, substance concentrations at specific locations of theskin (on the skin surface) and in depth (vertically in relation to thesurface) or relative to specific marker points on the skin can also bedetermined. Such marker points can be artificially applied points(visible or invisible markers applied on or in the skin) or naturalmarkers. Example of natural markers are the layer boundaries between theepidermis and dermis or a vein running through the tissue.

In particular, the values to be determined can not only be determinedwith spatial resolution, but also as an average value.

An especially advantageous variant of a calculation system is presentedbelow. It is recognisable for a person skilled in the art that amultitude of possibilities of implementation of the calculation sequenceor the supplementing or omission of calculation steps is possiblewithout diverging from the basic approach of the process.

The calculation process uses data that originates from the describeddetectors. These are essentially brightness values as well as values ofother sensors (such as temperature sensors and user input), that areused, for instance, as correction factors.

Step 1: Pre-Processing Correction

The normal pre-processing steps can be applied to the measurements andto virtual measurements that are explained below. These two types ofvalues are identified hereinafter as YS0. Typical examples forpre-processing steps include compensation for dark values, offsetcorrection or pulsed operation, the consideration of differentamplification factors or a linearity correction. In particular, acorrection based on known or estimated physical properties of the sampleis also possible. These can be measured, tabulated, or derived fromphysical models. In particular, different values, especially measurementvalues, can also be incorporated into the correction equations.

The obtained values should be identified in the following as YS1.

For simplification of the notation, the various YS1 values aresummarised in the description below. Of course, YS1 of each measurementvalue that has been taken is meant such that YS1 is representative forthe following values, e.g.:

-   -   YS1 brightness recorded by photodiode 1 when LED 1 illuminates    -   YS1 brightness recorded by photodiode 2 when LED 1 illuminates    -   YS1 brightness recorded by photodiode 1 when LED 2 illuminates    -   YS1 brightness recorded by photodiode 2 when LED 2 illuminates    -   YS1 brightness recorded by photodiode 10 when LED 20 illuminates    -   YS1 temperature of LED2    -   YS1 temperature of the skin    -   YS1 brightness recorded by photodiode 1 when LED 1 illuminates        measured at time 1    -   YS1 brightness recorded by photodiode 1 when LED 1 illuminates        measured at time 2    -   and so forth

Step 2: First Weighting

The information gathered from step 1 can be weighted; this is carriedout most easily by multiplying with a constant.

Weighting can also involve a non-linear function. Weighting withpolynomials is especially advantageous. Polynomials of the 4th degree ofthe form YS2=K3*YS1{circumflex over ( )}3+K2*YS1{circumflex over( )}2+K1*YS1+K0 are especially advantageous.

Additional advantageous is weighting with exponential functions of theform:

YS2=K4*K5{circumflex over ( )}(YS1*K6)

Logarithmic functions for similar applications purposes are also knownfrom the literature:

YS2=K7*LOG(K8*YS1;in base K9)

In an especially advantageous variant, a linear function defined sectionby section is used. Linear interpolation can take place between thestored support levels.

The functions can be selected with modelling of the problem. However, inmany cases the selection of the function and the parameters aredetermined with the extraction of a quantity of measurement values fromtest specimens or phantoms for which the correct result is known (e.g.,with a reference process). Then a computer iteratively tests whichcombinations of algorithms and constants are suitable for a goodrepresentation of the measured values based on the correct results.

This process also applies for the following steps in an advantageousvariant.

The constants can assume different values for each measurement. Thenotation of K is shown in a simplified form here, wherein sub-indexes ofK . . . are omitted.

An important variant of the weighting is temporal filtering. Inparticular, measurement values can be beneficially weighted usinglow-pass filters. For this purpose, the time of the measurement and thehistory of output values YS1 are included in the calculation in anadvantageous variant. The history of selected values is stored for thispurpose in an advantageous variant. Additional typical variants includediffusion equations that can describe the diffusion of substancesthrough the tissue and the resulting behaviour of concentrations overtime. They are often described differently by variants of exponentialfunctions, such as with differential equations.

Step 3: Compensation

The values obtained for YS2 from step 2 are now mathematically combinedwith each other so that disturbance variables or signals are omitted oremphasised.

Some new values YS3 are formed for this purpose.

The values YS3 are determined by means of summation in an advantageousvariant:

YS3=K101*YS2_(Index1) +K102*YS2_(Index2) + . . . Kxxx*YS2_(Index N)

In an alternative advantageous variant the YS3 are determined by productformation:

YS3=YS2_(Index1) {circumflex over ( )}K201*YS2_(Index2) {circumflex over( )}K202* . . . *YS2_(Index N) {circumflex over ( )}Kxxx

In this process, it may often be the case that different YS2calculations are used for the determining YS3 results. The YS2 are thuscalculated with partially different processing functions and differentconstant values.

The YS3 are determined in an advantageous variant such that theyrepresent specific properties of the sample to be studies with respectto specific locations or wavelengths.

An additional advantageous variant is the use of a neuronal network fordetermining YS3.

An additional advantageous variant is the determination of YS3 valueswith statistical processes. These are, for instance averagedetermination or median calculation. However, clustering processes canalso be applied to vectors from multiple YS2. An example is thedescribed recognition and weighting of outliers based on known standarddeviations. Kalman or Wiener filters are also examples.

An especially advantageous variant incorporates the geometric factors ofthe emitter detector arrangement into the process. This includesdistances of locations of light transmission and light reception, aswell as the expected optical paths of the photons passing through thesample. Since the volume through which the light passes depends onscattering and absorption and this can be parameters determined,implementing a dependency of the volumes on YS0 and YS3 is advantageous.It is often advantageous to calculate which volumes the light of anLED/light receiver combination have in common and which they do not havein common and determine the averaging factors therefrom.

Processes for classic image processing can also be applied.

In an especially advantageous variant, YS2, the comparableemitter-detector pairs belonging to a group are each summarised as atleast one YS3. In an advantageous variant these YS3 are virtualmeasurement values, as explained in step 4. In an advantageous variant,these virtual measurement values are then summarised in an additionalstep 3 in order to determine the resulting concentration valuetherefrom.

Step 4: Obtaining Virtual Measurement Values

Some of the YS3 are now defined as virtual measurement values. Steps 1to 4 can be executed again using these values.

This is an advantageous method because similar calculations can alwaysserve as a basis for obtaining the calculation result. In particular,automatic determination of the calculation functions and the constantsto be used in the calculation are made significantly easier as a result.

In many cases, multiple effects must be compensated for in order toobtain the end result.

For example, undesired effects of diverse blood circulation of the testspecimen can be compensated for by carrying out steps 1-4 a first time.

By returning the results YS3 to additional YS0 values, measurementdeviations based on varying surface coupling can be equalised byconducting steps 1 to 4 a second time.

Then the general tissue absorptions can be then separated from theabsorption of an interesting substance (e.g., carotenoids) by conductingsteps 1 to 4 a third time.

Finally, one or multiple concentration values of an interestingsubstance calculated in this manner can be allocated to a physiologicalvalue by performing steps 1 to 4 a fourth time. This can, for instance,be a recommendation for future behaviour, such as described in thefollowing two examples.

Example 1: The Fitness Value of the Skin is X (Wherein X Originates froma Scale from 1 to 10) Example 2: The Probability that Tomatoes ConsumedDuring the Next Meal Will Promote the Health by a Specific Value is xxx%

The processing of life circumstances that have been input or detected inanother manner as YS0 values is also particularly advantageous for suchstatements.

In order to be able to apply steps 1 to 4 repeatedly, it must bedetermined which YS3 values are output to the user, and which are onlyused as intermediate variables.

In an advantageous variant, some of the processes and constants, as wellas the number of YS3 that are used are specified by the person such thatthe known system (e.g., the human skin and the device that is used) isdescribed. The other constants are determined by a computer, e.g., basedon a measurement with the test specimen or phantoms in which correctvalues obtained per reference are present. The processes for this can bePLS (Partial Least Squares), main component analysis, geneticalgorithms, or systematic sampling.

In an advantageous variant, the system can also be trained to YS3intermediate results that are obtained with a reference measurement.This can be, for instance, the scatter and absorption coefficients ofskin that have been measured based on samples. As is known, thesevariables are important for measurements on human skin, such as thecarotenoid measurement, and are thus a useful variable in order todefine them as an intermediate variable and to train the recognitionthereof separately before the actual output variable is trained.Therefore, processes and groups of constants can also be kept constantduring the training process of the output value, whereas others areavailable for purposeful iterative modification.

In an advantageous variant, the YS3 represent concentration values of asubstance at a specific depth in the sample, especially a skin sample.

The described evaluation process offers decisive advantages for thedescribed device. FIG. 10 shows an example configuration of a device.This comprises 100 light emitters and 40 light detectors. In addition,this is evaluated repeatedly for a measurement such that 20,000measurement values are obtained. Manual creation of the evaluationalgorithm for such a large number of measurement values is hardlypossible without the use of a basic framework as described above.However, with the use of the algorithm framework described above,determination of the algorithm and constants with computer-assistedoptimisation processes is possible.

The present invention is not limited to embodiments described herein;reference should be made to the appended claims.

1. (canceled)
 2. A sensor for non-invasively measuring physiologicalparameters or substance concentrations in human tissue including humanskin, the sensor comprising: a circuit board comprising a first side; aplurality of emitters each comprising a semiconductor component that isconfigured to emit light; a plurality of detectors each comprising asemiconductor component configured to determine a quantity of lightarriving at the plurality of detectors; a light barrier element arrangedon the first side of the circuit board and comprising non-transparentmaterial, the light barrier element forming: a first light barrierelement surface adjacent to the first side of the circuit board; asecond light barrier element surface; and a plurality of cavities thatincludes a first cavity, a second cavity, a third cavity, a fourthcavity, a fifth cavity, and a sixth cavity; and a contact elementmounted to the second light barrier element surface, the contact elementcomprising a transparent material and a non-transparent material, thecontact element forming a contact surface configured to be brought intocontact with human tissue, wherein: within each of the first cavity, thesecond cavity, and the third cavity one or more emitters of theplurality of emitters are mounted to the first side of the circuit boardsuch that light with at least three different wavelength characteristicsis configured to be emitted from each of the first cavity, the secondcavity, and the third cavity; and within each of the fourth cavity, thefifth cavity, and the sixth cavity one or more detectors of theplurality of detectors are mounted to the first side of the circuitboard.
 3. The sensor of claim 2, wherein there is one cavity of theplurality of cavities in which a temperature sensor and an emitter ofthe plurality of emitters is arranged.
 4. The sensor of claim 3 furthercomprising an element to influence a direction in which photons areemitted into the human tissue, the element comprising a lens.
 5. Thesensor of claim 4, wherein the plurality of semiconductor components ofthe plurality of emitters and the plurality of semiconductor componentsof the plurality of detectors comprise semiconductor components ofrectangular geometry that are located less than 6 mm from the human skinwhen the human skin is in contact with the contact surface.
 6. Thesensor of claim 5, wherein the sensor is integrated into a device withwhich a user regularly comes into contact.
 7. The sensor of claim 6,wherein the contact surface is curved.
 8. A sensor for non-invasivelymeasuring physiological parameters or substance concentrations in humantissue including human skin, the sensor comprising: a circuit boardcomprising a first side; a plurality of emitters each comprising asemiconductor component that is configured to emit light, at least threeof the plurality of emitters arranged in a planar arrangement on thefirst side of the circuit board; a plurality of detectors eachcomprising a semiconductor component configured to determine a quantityof light arriving at the plurality of detectors, at least three of theplurality of detectors arranged in a planar arrangement on the firstside of the circuit board; one or more non-transparent materials; and acontact element comprising a transparent material and at least one ofthe one or more non-transparent materials, the contact element forming acontact surface configured to be brought into contact with human tissueto perform non-invasive measurements of physiological parameters orsubstance concentrations in the human tissue, wherein: there is aplurality of emitter-detector pairs, each emitter-detector pairincluding an emitter of the plurality of emitters and a detector of theplurality of detectors, each emitter-detector pair being characterizedby an emitter-detector wavelength characteristic corresponding to awavelength characteristic of the light emitted by the emitter anddetected by the detector in the emitter-detector pair and anemitter-detector distance corresponding to a distance between theemitter and the detector in the emitter-detector pair, there are atleast three emitter-detector pairs with emitter-detector wavelengthcharacteristics that differ from one another, there are at least twoemitter-detector pairs with emitter-detector distances that differ fromone another, there is a first emitter-detector pair and a secondemitter-detector pair with the same emitter-detector distance and thesame emitter-detector wavelength characteristic and a first straightline passing through the emitter and the detector of the firstemitter-detector pair and a second straight line passing through theemitter and the detector of the second emitter-detector pair form anangle that is greater than 45 degrees and less than or equal to 90degrees, and at least one of the one or more non-transparent materialsis arranged in such a way that, when the contact surface is completelycovered by the human tissue, light emitted by the at least threeemitters reaches one of the at least three detectors only by passingthrough the human tissue covering the contact surface.
 9. The sensor ofclaim 8, wherein: there are groups of equal emitter-detector pairs, agroup of equal emitter-detector pairs comprising at least twoemitter-detector pairs with approximately the same emitter-detectorwavelength characteristic and approximately the same emitter-detectordistance, and each detector is the detector in at least sixemitter-detector pairs and each of the at least six emitter-detectorpairs is in one of the groups of equal emitter-detector pairs.
 10. Thesensor of claim 9, wherein each emitter is the emitter in at least twoemitter-detector pairs and each of the at least two emitter-detectorpairs is in one of the groups of equal emitter-detector pairs.
 11. Thesensor of claim 10, wherein for each group of equal emitter-detectorpairs, a plurality of oriented lines can be formed with each orientedline pointing from an emitter to a detector of an emitter-detector pairin the group of equal pairs, the plurality of oriented lines includingat least four orientations that are distributed approximately equallyover an angular range from 0 to 360 degrees.
 12. The sensor of claim 11,wherein for each wavelength there is at least one group ofemitter-detector pairs in which there are eight orientations fromemitter to detector which are approximately equally distributed over theangular range from 0 to 360 degrees.
 13. The sensor of claim 12 wherein:a first group of equal emitter-detector pairs has a firstemitter-detector pair of the first group and a second emitter-detectorpair of the first group and a directional characteristic of photonemission of the emitter of the first emitter-detector pair of the firstgroup relative to the detector of the first emitter-detector pair of thefirst group is different from a directional characteristic of photonemission of the emitter of the second emitter-detector pair of the firstgroup relative to the detector of the second emitter-detector pair ofthe first group, and the directional characteristic being determined bya quantity of photons leaving the sensor in each direction.
 14. Thesensor of claim 8, wherein: there are at least four emitter cavitieswhich each contain a first emitter emitting a first wavelength, a secondemitter emitting a second wavelength, and a third emitter emitting athird wavelength, there are at least four detectors, there are groups ofequal emitter-detector pairs, a group of equal emitter-detector pairscomprising at least two emitter-detector pairs with approximately thesame emitter-detector wavelength characteristic and approximately thesame emitter-detector distance, there are at least six groups of equalemitter-detector pairs with each group containing at least a firstemitter-detector pair, a second emitter-detector pair, a thirdemitter-detector pair, and a fourth emitter-detector pair, for eachemitter-detector pair in a group of equal emitter-detector pair, thereis an area defined by all points in a plane of emitters and detectorsthat have less than 1 mm distance to a line connecting the emitter andthe detector, at least 95% of the area for the first emitter-detectorpair does not overlap with the area of the second emitter-detector pairof each group, and at least 95% of the area for the thirdemitter-detector pair does not overlap with the area of the fourthemitter-detector pair of each group.
 15. A method for non-invasivelymeasuring physiological parameters or substance concentrations in humantissue including human skin using a sensor, the method comprising:emitting light from each of at least three emitters with a portion ofthe emitted light penetrating into the human tissue to be non-invasivelymeasured; detecting light with each of at least three detectors, thelight arriving at the at least three detectors after penetrating intothe human tissue and interacting with the human tissue, being partlyscattered and partly absorbed by the human tissue, the detected lightbeing light that has been scattered in the human tissue in such a waythat it leaves the human tissue and arrives at the at least threedetectors; blocking a portion of the light emitted from each of the atleast three emitters using a non-transparent material, thenon-transparent material arranged such that a majority of the lightemitted by the at least three emitters and detected by the at leastthree detectors passed through a portion of the human tissue; performinga measurement sequence that includes activating emitters of the at leastthree emitters in successive steps and detectors of the at least threedetectors measure brightness values of detected light in each step ofthe successive steps; recording a set of measurement values thatincludes values measured by the at least three detectors in themeasurement sequence; determining one or more physiological parametersor substance concentrations using the set of measurement values; andmeasuring coupling of contact between the human tissue and the sensor,wherein: the at least three emitters and the at least three detectorsare located in a single plane in a planar arrangement, the at leastthree emitters are configured to emit a majority of photons in adirection forming an angle of at least 5 degrees to the single plane inwhich the at least three emitters and the at least three detectors arelocated, and the at least three light emitters are configured to emit atleast three different wavelength characteristics.
 16. The method ofclaim 15, wherein, responsive to measuring insufficient coupling betweenthe human tissue and the sensor: aborting the measurement sequence; andgenerating a notification of insufficient coupling.
 17. The method ofclaim 15, wherein a detector of the at least three detectors isconfigured to detect photons emitted by at least two emitters of the atleast three emitters that have different wavelength characteristics. 18.The method of claim 17, wherein the at least three emitters and the atleast three detectors are located in a plurality of cavities formed bythe non-transparent material.
 19. The method of claim 18, wherein theplurality of cavities is cast with transparent material.
 20. The methodof claim 18, wherein: at least four cavities of the plurality ofcavities each contain three emitters that have different wavelengthcharacteristics, and at least 4 cavities of the plurality of cavitiescontain a detector.
 21. The method of claim 18, wherein there is atleast one cavity of the plurality of cavities that contains a firstemitter of the at least three emitters and the method further includescausing the first emitter to emit light towards a first detector of theat least three detectors with a steep exit angle and towards a seconddetector of the at least three detectors with a steep and flat exitangle.
 22. The method of claim 15, wherein a portion of thenon-transparent material is filled into a slit made in transparentmaterial.